fix: added missing check on null values, closes #3519

Author: thorsten

phpmyfaq/src/phpMyFAQ/Faq/Permission.php

@@ -151,7 +151,9 @@ public function createPermissionArray(): array
                 ];
             } else {
                 $permissions += [
-                    'restricted_user' => Filter::filterArray($data->restricted_users, FILTER_VALIDATE_INT),
+                    'restricted_user' => is_array($data->restricted_users)
+                        ? Filter::filterArray($data->restricted_users, FILTER_VALIDATE_INT)
+                        : [],
                 ];
             }
         }
@@ -167,7 +169,9 @@ public function createPermissionArray(): array
                 ];
             } else {
                 $permissions += [
-                    'restricted_groups' => Filter::filterArray($data->restricted_groups, FILTER_VALIDATE_INT)
+                    'restricted_groups' => is_array($data->restricted_groups)
+                        ? Filter::filterArray($data->restricted_groups, FILTER_VALIDATE_INT)
+                        : [],
                 ];
             }
         }