Handling the empty list of update sensors, and error check before setting the...

Handling the empty list of update sensors, and error check before setting the sampling strategies included.

epl_katcp/epl_katcp_client.py

@@ -250,8 +250,9 @@ class KatcpClient(katcp.DeviceClient):
                               format(self.SENSOR_MAP[sensor_name].name,
                                      self.update_sensors_dict[sensor_name]['strategy'],
                                      self.sampling_strategy_param_number[self.update_sensors_dict[sensor_name]['strategy']],
-                                     len(self.update_sensors_dict[sensor_name]['params'])
-                                     ))
+                                     len(list(filter(None,
+                                         self.update_sensors_dict
+                                         [sensor_name]['params'].split(' '))))))
                         self.send_request("?sensor-sampling {} period {}".
                                           format(sensor_name,
                                                  self._refresh_interval))