return empty result in aggregator if no GPUs were used

db/influx/influxdb_fetchgpu.py

@@ -152,6 +152,7 @@ def parse_gpu_used(data):
         if "statement_id" in data[0]:
             if conf.DEBUG:
                 print("Could not execute query to get used GPUs", queries[sid])
+            return {}
         else:
             raise RuntimeError("Cannot parse the output of GPU count query", data[i])