Bug: OpenEMS Counter/Inverter not working properly

[martingruening]

Setup:

• openEMS Release 2024.1
• openWB Standard+ with Software2 2024-01-03 12:21:20 +0100 [06bcf54f9]
• OpenEMS counter (DeviceFemsCounter) properly set up (showing voltage, frequency etc.)

Error Message in Status on the Counter and Inverter:

`Modulmeldung:`
<class 'TypeError'> unsupported operand type(s) for *: 'NoneType' and `'int'

Result:

• Charging is blocked, device not working as expected

Log:

2024-02-01 06:20:20,345 - {modules.common.fault_state:55} - {ERROR:device0} - openEMS Zähler: FaultState FaultStateLevel.ERROR, FaultStr <class 'TypeError'> unsupported operand type(s) for *: 'NoneType' and 'int', Traceback: 
Traceback (most recent call last):
  File "/var/www/html/openWB/packages/modules/common/configurable_device.py", line 36, in __call__
    self.__updater(components_list)
  File "/var/www/html/openWB/packages/modules/devices/fems/device.py", line 32, in update_components
    component.update(session)
  File "/var/www/html/openWB/packages/modules/devices/fems/inverter.py", line 21, in update
    power = scale_metric(response["value"], response.get("unit"), 'W') * -1
TypeError: unsupported operand type(s) for *: 'NoneType' and 'int'