Prevent crash for firmware updater if the activePrinter is not set

plugins/FirmwareUpdater/FirmwareUpdaterMachineAction.py

@@ -57,7 +57,7 @@ class FirmwareUpdaterMachineAction(MachineAction):
     outputDeviceCanUpdateFirmwareChanged = pyqtSignal()
     @pyqtProperty(QObject, notify = outputDeviceCanUpdateFirmwareChanged)
     def firmwareUpdater(self) -> Optional["FirmwareUpdater"]:
-        if self._active_output_device and self._active_output_device.activePrinter.getController().can_update_firmware:
+        if self._active_output_device and self._active_output_device.activePrinter and self._active_output_device.activePrinter.getController().can_update_firmware:
             self._active_firmware_updater = self._active_output_device.getFirmwareUpdater()
             return self._active_firmware_updater