Add none check

Author: pierotofy

app/api/workers.py

@@ -20,7 +20,7 @@ def get(self, request, celery_task_id=None, **kwargs):
             out = {'ready': False}
 
             # Copy progress meta
-            if res.state == "PROGRESS":
+            if res.state == "PROGRESS" and res.info is not None:
                 for k in res.info:
                     out[k] = res.info[k]