Fixes #7551: General Error. Access to undefined index

extension/Source/core/database/Database.php

@@ -324,9 +324,8 @@ class Database {
         }
 
         // Look for missing '()' after FROM in case LEFT JOIN is used.
-        if (stripos($errorMsg, 'Unknown column') !== false &&
-            stripos($pos = $sql, ' LEFT JOIN ') !== false &&
-            isset($sql[$pos - 1]) && $sql[$pos - 1] != ')') {
+        $pos = stripos($sql, ' LEFT JOIN ');
+        if (stripos($errorMsg, 'Unknown column') !== false && $pos !== false && ($sql[$pos - 1] ?? '') != ')') {
             $msg .= "HINT: Maybe the tables after 'FROM' should be enclosed by '()' \n";
         }