common: fixed activity result on succes

circle/common/models.py

@@ -64,6 +64,7 @@ class ActivityModel(TimeStampedModel):
         if not self.finished:
             self.finished = timezone.now()
             self.succeeded = succeeded
+            if result is not None:
                 self.result = result
             if event_handler is not None:
                 event_handler(self)