Fix Controller.run bug when no input is available

geomagio/Controller.py

@@ -290,7 +290,7 @@ class Controller(object):
             channels=input_channels,
             interval=input_interval,
         )
-        if not algorithm.can_produce_data(
+        if not timeseries or not algorithm.can_produce_data(
             starttime=timeseries[0].stats.starttime,
             endtime=timeseries[0].stats.endtime,
             stream=timeseries,