rel #18026: Prevent hasLocalPermissionOn from crashing when no permission is given.

library/Class/UserGroup.php

@@ -387,9 +387,10 @@ class Class_UserGroup extends Storm_Model_Abstract {
 
 
 	public function hasLocalPermissionOn($permission, $model) {
-		return 0 < Class_UserGroup_Permission::countBy(['id_group' => $this->getId(),
-																										'id_permission' => $permission->getId(),
-																										'id_model' => $model->getId()]);
+		return $permission && $model
+			&& 0 < Class_UserGroup_Permission::countBy(['id_group' => $this->getId(),
+																									'id_permission' => $permission->getId(),
+																									'id_model' => $model->getId()]);
 	}