Merge pull request #7027 from readthedocs/check-for-none

Task Router: check for None

Author: stsewd

readthedocs/builds/tasks.py

@@ -82,7 +82,7 @@ def route_for_task(self, task, args, kwargs, **__):
 
         # Build time average is high
         length_avg = queryset.filter(pk__in=last_builds).aggregate(Avg('length')).get('length__avg')
-        if length_avg > self.TIME_AVERAGE:
+        if length_avg and length_avg > self.TIME_AVERAGE:
             log.info(
                 'Routing task because project has high time average. queue=%s',
                 self.BUILD_LARGE_QUEUE,