diff --git a/objects/mysql_dal.php b/objects/mysql_dal.php
index 2bc58644ea..675109f8fa 100644
--- a/objects/mysql_dal.php
+++ b/objects/mysql_dal.php
@@ -208,7 +208,7 @@ class sqlDAL
              *
              */
 
-             _error_log("writeSql [{$stmt->errno}] {$stmt->error} ".' '.json_encode(debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS))) . " userAgent=[{$_SERVER['HTTP_USER_AGENT']}]";
+             _error_log(sprintf('writeSql [%s] {%s}  %s userAgent=[%s]', $stmt->errno, $stmt->error, json_encode(debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS)), $_SERVER['HTTP_USER_AGENT'] ?? '-'));
              if($stmt->errno == 1205 && preg_match('/CachesInDB/', $preparedStatement)){//Lock wait timeout exceeded; try restarting transaction
                 _error_log("writeSql Recreate CachesInDB ");
                 $sql = 'DROP TABLE IF EXISTS `CachesInDB`';
diff --git a/plugin/Cache/Cache.php b/plugin/Cache/Cache.php
index f34fb1e95a..521f6e8a01 100644
--- a/plugin/Cache/Cache.php
+++ b/plugin/Cache/Cache.php
@@ -467,9 +467,11 @@ class Cache extends PluginAbstract {
 
         $rows = Cache_schedule_delete::getAll();        
         Cache_schedule_delete::truncateTable();
-        foreach ($rows as $row) {
-            CacheDB::deleteCacheStartingWith($row['name'], false);
-            self::deleteCacheDir($row['name']);
+        if (is_iterable($rows)) {
+            foreach ($rows as $row) {
+                CacheDB::deleteCacheStartingWith($row['name'], false);
+                self::deleteCacheDir($row['name']);
+            }
         }
     }