diff --git a/lam/lib/modules.inc b/lam/lib/modules.inc
index 0458f481c..4a3992232 100644
--- a/lam/lib/modules.inc
+++ b/lam/lib/modules.inc
@@ -671,13 +671,16 @@ function getRequiredExtensions() {
  * meta HTML code. This allows to have a common design for all module pages.
  *
  * @param string|null $module Name of account module
- * @param htmlElement|htmlElement[] $input htmlElement or array of htmlElement elements
+ * @param htmlElement|htmlElement[]|null $input htmlElement or array of htmlElement elements
  * @param array $values List of values which override the defaults in $input (name => value)
  * @param boolean $restricted If true then no buttons will be displayed
  * @param string|null $scope Account type
  * @return array List of input field names and their type (name => type)
  */
 function parseHtml($module, $input, $values, $restricted, $scope) {
+	if ($input === null) {
+		return [];
+	}
 	if ($input instanceof htmlElement) {
 		return $input->generateHTML($module, $input, $values, $restricted, $scope);
 	}
diff --git a/lam/lib/modules/fixed_ip.inc b/lam/lib/modules/fixed_ip.inc
index d53a932e4..d3f6f2839 100644
--- a/lam/lib/modules/fixed_ip.inc
+++ b/lam/lib/modules/fixed_ip.inc
@@ -911,7 +911,7 @@ class fixed_ip extends baseModule {
 	 */
 	public function getListRenderFunction(string $attributeName): ?callable {
 		if ($attributeName === 'fixed_ips') {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				// find all fixed addresses:
 				$entries = searchLDAP($entry['dn'], 'objectClass=dhcpHost', ['dhcpstatements', 'dhcphwaddress', 'cn']);
 				if (count($entries) > 0) {
@@ -959,7 +959,7 @@ class fixed_ip extends baseModule {
 					}
 					return $group;
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/lib/modules/imapAccess.inc b/lam/lib/modules/imapAccess.inc
index 73494f0e1..e78186fa0 100644
--- a/lam/lib/modules/imapAccess.inc
+++ b/lam/lib/modules/imapAccess.inc
@@ -411,7 +411,7 @@ class imapAccess extends baseModule {
 	/**
 	 * Creates the mailbox for a user.
 	 *
-	 * @param Horde_Imap_Client_Socket $client IMAP client
+	 * @param Client $client IMAP client
 	 * @param string $userName user name
 	 * @param string $email_domain email domain
 	 * @return array error messages
@@ -452,7 +452,7 @@ class imapAccess extends baseModule {
 	/**
 	 * Sets the mailbox quota for a user.
 	 *
-	 * @param Horde_Imap_Client_Socket $client IMAP client
+	 * @param Client $client IMAP client
 	 * @param string $userName user name
 	 * @param string $email_domain email domain
 	 * @param string $quota mailbox quota
@@ -927,27 +927,31 @@ class imapAccess extends baseModule {
 	/**
 	 * Returns if the mailbox exists.
 	 *
-	 * @param $client IMAP client
+	 * @param Client $client IMAP client
 	 * @param string $path mailbox path
 	 * @return bool is existing
 	 */
 	private function isMailboxExisting($client, string $path): bool {
 		$list = $client->getConnection()->folders($path);
-		return ($list !== null) && is_array($list->data()) && (count($list->data()) >= 1);
+		return is_array($list->data()) && (count($list->data()) >= 1);
 	}
 
 	/**
 	 * Returns the quota data for the user.
 	 *
-	 * @param $client IMAP client
+	 * @param Client $client IMAP client
 	 * @param string $user user name
 	 * @return array array with keys QUOTA_USAGE and QUOTA_LIMIT
 	 */
 	private function getQuota($client, string $user): array {
-		$user = $client->getConnection()->escapeString($user);
+		$connection = $client->getConnection();
+		if (!($connection instanceof ImapProtocol)) {
+			return [];
+		}
+		$user = $connection->escapeString($user);
 		$quota_values = [];
 		try {
-			$quota = $client->getConnection()->requestAndResponse('GETQUOTA', [$user]);
+			$quota = $connection->requestAndResponse('GETQUOTA', [$user]);
 			$quota = $quota->data();
 			if (isset($quota[0][2][0]) && ($quota[0][2][0] === 'STORAGE')) {
 				$quota_values = [
diff --git a/lam/lib/modules/inetOrgPerson.inc b/lam/lib/modules/inetOrgPerson.inc
index b0fd58312..968e4544d 100644
--- a/lam/lib/modules/inetOrgPerson.inc
+++ b/lam/lib/modules/inetOrgPerson.inc
@@ -4138,7 +4138,7 @@ class inetOrgPerson extends baseModule implements passwordService, AccountStatus
 			};
 		}
 		elseif ($attributeName === 'jpegphoto') {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (isset($entry[$attribute][0]) && ($entry[$attribute][0] !== '')) {
 					if (strlen($entry[$attribute][0]) < 100) {
 						// looks like we have read broken binary data, reread photo
@@ -4162,7 +4162,7 @@ class inetOrgPerson extends baseModule implements passwordService, AccountStatus
 					$image->setCSSClasses(['thumbnail']);
 					return $image;
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/lib/modules/range.inc b/lam/lib/modules/range.inc
index c4296f2eb..b025b7151 100644
--- a/lam/lib/modules/range.inc
+++ b/lam/lib/modules/range.inc
@@ -820,7 +820,7 @@ class range extends baseModule {
 	 */
 	public function getListRenderFunction(string $attributeName): ?callable {
 		if ($attributeName === 'dhcprange') {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (!empty($entry[$attribute][0])) {
 					$table = new htmlTable();
 					$table->setCSSClasses(['nowrap']);
@@ -861,7 +861,7 @@ class range extends baseModule {
 					}
 					return $table;
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/lib/modules/sambaSamAccount.inc b/lam/lib/modules/sambaSamAccount.inc
index 4fec23dd6..7e529bf61 100644
--- a/lam/lib/modules/sambaSamAccount.inc
+++ b/lam/lib/modules/sambaSamAccount.inc
@@ -3089,7 +3089,7 @@ class sambaSamAccount extends baseModule implements passwordService, AccountStat
 	 */
 	public function getListRenderFunction(string $attributeName): ?callable {
 		if ($attributeName === 'sambakickofftime') {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (!empty($entry[$attribute][0])) {
 					if ($entry[$attribute][0] > 2147483648) {
 						return new htmlOutputText("∞");
@@ -3099,7 +3099,7 @@ class sambaSamAccount extends baseModule implements passwordService, AccountStat
 						return new htmlOutputText($date->format('d.m.Y'));
 					}
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/lib/modules/shadowAccount.inc b/lam/lib/modules/shadowAccount.inc
index 2391f9e91..d54358bd7 100644
--- a/lam/lib/modules/shadowAccount.inc
+++ b/lam/lib/modules/shadowAccount.inc
@@ -1036,12 +1036,12 @@ class shadowAccount extends baseModule implements passwordService, AccountStatus
 	 */
 	public function getListRenderFunction(string $attributeName): ?callable {
 		if (($attributeName === 'shadowexpire') || ($attributeName === 'shadowlastchange')) {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (!empty($entry[$attribute][0])) {
 					$time = new DateTime('@' . $entry[$attribute][0] * 24 * 3600, getTimeZone());
 					return new htmlOutputText($time->format('d.m.Y'));
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/lib/modules/windowsGroup.inc b/lam/lib/modules/windowsGroup.inc
index 11ffea3d4..65175f63f 100644
--- a/lam/lib/modules/windowsGroup.inc
+++ b/lam/lib/modules/windowsGroup.inc
@@ -1126,7 +1126,7 @@ class windowsGroup extends baseModule {
 			};
 		}
 		elseif (($attributeName === 'managedby') || ($attributeName === 'member')) {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (!empty($entry[$attribute][0])) {
 					$typeManager = new TypeManager();
 					$values = $entry[$attribute];
@@ -1149,7 +1149,7 @@ class windowsGroup extends baseModule {
 					}
 					return new htmlDiv(null, new htmlOutputText(implode('<br>', $values), false), ['rightToLeftText']);
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/lib/modules/windowsHost.inc b/lam/lib/modules/windowsHost.inc
index d2cf8088d..a78267fb1 100644
--- a/lam/lib/modules/windowsHost.inc
+++ b/lam/lib/modules/windowsHost.inc
@@ -414,7 +414,7 @@ class windowsHost extends baseModule {
 			};
 		}
 		elseif ($attributeName === 'managedby') {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (!empty($entry[$attribute][0])) {
 					$value = $entry[$attribute][0];
 					$typeManager = new TypeManager();
@@ -431,7 +431,7 @@ class windowsHost extends baseModule {
 					}
 					return new htmlDiv(null, new htmlOutputText($value, false), ['rightToLeftText']);
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/lib/modules/windowsUser.inc b/lam/lib/modules/windowsUser.inc
index af362454b..bd07b822f 100644
--- a/lam/lib/modules/windowsUser.inc
+++ b/lam/lib/modules/windowsUser.inc
@@ -4808,7 +4808,7 @@ class windowsUser extends baseModule implements passwordService, AccountStatusPr
 			};
 		}
 		elseif (($attributeName === 'jpegphoto') || ($attributeName === 'thumbnailphoto')) {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (isset($entry[$attribute][0]) && ($entry[$attribute][0] !== '')) {
 					if (strlen($entry[$attribute][0]) < 100) {
 						// looks like we have read broken binary data, reread photo
@@ -4832,7 +4832,7 @@ class windowsUser extends baseModule implements passwordService, AccountStatusPr
 					$image->setCSSClasses(['thumbnail']);
 					return $image;
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		elseif ($attributeName === 'accountexpires') {
@@ -4848,7 +4848,7 @@ class windowsUser extends baseModule implements passwordService, AccountStatusPr
 			};
 		}
 		elseif ($attributeName === 'manager') {
-			return function(array $entry, string $attribute): ?htmlElement {
+			return function(array $entry, string $attribute): htmlElement {
 				if (!empty($entry[$attribute][0])) {
 					$value = $entry[$attribute][0];
 					$typeManager = new TypeManager();
@@ -4865,7 +4865,7 @@ class windowsUser extends baseModule implements passwordService, AccountStatusPr
 					}
 					return new htmlDiv(null, new htmlOutputText($value, false), ['rightToLeftText']);
 				}
-				return null;
+				return new htmlGroup();
 			};
 		}
 		return null;
diff --git a/lam/templates/tests/schemaTest.php b/lam/templates/tests/schemaTest.php
index 2e35fa61e..63558cdd2 100644
--- a/lam/templates/tests/schemaTest.php
+++ b/lam/templates/tests/schemaTest.php
@@ -6,6 +6,7 @@ use \htmlStatusMessage;
 use \htmlSubTitle;
 use \htmlOutputText;
 use \htmlImage;
+use LAM\SCHEMA\ObjectClass;
 use function \LAM\SCHEMA\get_schema_objectclasses;
 use function \LAM\SCHEMA\get_cached_schema;
 /*
diff --git a/phpstan.neon b/phpstan.neon
index b234094a3..60a4350fd 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -15,7 +15,6 @@ parameters:
 		analyseAndScan:
 			- */lists/changePassword.php
 	ignoreErrors:
-		- '#.* on an unknown class .*#'
 		- '#.* has invalid type .*#'
 		- '#Function [a-zA-Z0-9\\_-]+ not found.#'
 		- '#Used function [a-zA-Z0-9\\_-]+ not found.#'