Fix regression bug with 0 meetings

bbbmon/meetings.py

@@ -225,7 +225,7 @@ def sum_meetings(config: Config, meetings:  Optional[XmlDictConfig]) ->  Optiona
     active_endpoints = [m for m in meetings if m != ["unreachable"]]
 
     if len(active_endpoints) == 0:
-        return None
+        return config, None
 
     summed_endpoint =  []