Fix error when TestRailAPI returns a None instead of result comment
PRODX-37098

Change-Id: I0afbe58957855ace6ab31f0bc2b4b30bcd5ffe06
diff --git a/testrail_bot/control/celery_tasks/testrail_pipeline.py b/testrail_bot/control/celery_tasks/testrail_pipeline.py
index 84ed930..5f7e7c4 100644
--- a/testrail_bot/control/celery_tasks/testrail_pipeline.py
+++ b/testrail_bot/control/celery_tasks/testrail_pipeline.py
@@ -28,6 +28,9 @@
     :param test_run: TestRun object that contains switchers for filters
     :return: modified text
     """
+    if not data:
+        data = ""
+
     if test_run.filter_last_traceback:
         data = filters.last_traceback_filter(data)