diff --git a/common/services/TaskService.php b/common/services/TaskService.php
index ad2719b..2db1cb0 100644
--- a/common/services/TaskService.php
+++ b/common/services/TaskService.php
@@ -42,7 +42,7 @@ class TaskService
     {
         $modelTask = ProjectTask::findOne($task_params['task_id']);
 
-        if ($task_params['executor_id'] == 0){
+        if (isset($task_params['executor_id']) && $task_params['executor_id'] == 0){
             $task_params['executor_id'] = null;
         }