fix: ErrorException : Undefined variable $filterClasses

Author: kenjis

system/Test/FilterTestTrait.php

@@ -125,17 +125,17 @@ protected function getFilterCaller($filter, string $position): Closure
             throw new InvalidArgumentException('Invalid filter position passed: ' . $position);
         }
 
+        $filterClasses = [$filter];
+
         if (is_string($filter)) {
             // Check for an alias (no namespace)
             if (strpos($filter, '\\') === false) {
                 if (! isset($this->filtersConfig->aliases[$filter])) {
                     throw new RuntimeException("No filter found with alias '{$filter}'");
                 }
 
-                $filterClasses = $this->filtersConfig->aliases[$filter];
+                $filterClasses = (array) $this->filtersConfig->aliases[$filter];
             }
-
-            $filterClasses = (array) $filterClasses;
         }
 
         foreach ($filterClasses as $class) {