call relationship directly to allow deletes with lazy loading disabled

Author: lukasleitsch

src/CascadeSoftDeletes.php

@@ -117,7 +117,7 @@ protected function getCascadingDeletes()
     protected function getActiveCascadingDeletes()
     {
         return array_filter($this->getCascadingDeletes(), function ($relationship) {
-            return ! is_null($this->{$relationship});
+            return ! is_null($this->{$relationship}());
         });
     }
 }