fix: Fix PHPStan error

Author: jose-bittacora

src/DiagramElement/RelationsFilter.php

@@ -2,6 +2,7 @@
 
 namespace Smeghead\PhpClassDiagram\DiagramElement;
 
+use InvalidArgumentException;
 use Smeghead\PhpClassDiagram\Config\Options;
 use Smeghead\PhpClassDiagram\Enums\DependenciesDirection;
 use function preg_match;
@@ -98,6 +99,11 @@ public function filterClasses(array $filteredClasses, string $direction): array
     function getFilteringRegex(string $filteredClass, string $direction): string
     {
         $filteredClass = str_replace('*', '.*?', $filteredClass);
+
+        if (!in_array($direction, ['out', 'in'])) {
+            throw new InvalidArgumentException("Invalid direction '$direction'");
+        }
+
         return match ($direction) {
             'in' => "/.*?> ({$filteredClass}$|[\w_]+{$filteredClass}$)/",
             'out' => "/^({$filteredClass}|^[\w_]+{$filteredClass}) .*?>.*?/",