deviceMethodWidget.py: fix mypy complaints

kamzik3/gui/deviceMethodWidget.py

@@ -40,7 +40,7 @@ class DeviceMethodWidget(Ui_Form, DeviceWidget, StackableWidget):
         parent=None,
     ):
         self.method = method
-        self.value_controls = ()
+        self.value_controls: Tuple[QWidget, ...] = ()
         DeviceWidget.__init__(
             self, device, model_image=model_image, config=config, parent=parent
         )
@@ -287,24 +287,26 @@ class MethodEnabledByAttributeWidget(DeviceMethodEnabledWidget):
 
         # emit a signal each time the external trigger value is changed
         # callback(attribute_object[key_filter]) is called
-        self.device.attach_attribute_callback(
-            attribute=ATTR_EXTERNAL_TRIGGER,
-            callback=self.sig_control_changed.emit,
-            key_filter=VALUE,
-        )
-
-        # define the status of the input field using the current value of the attribute
-        self.control_changed(self.device.get_value(ATTR_EXTERNAL_TRIGGER))
-
-        # create the checkbox for the attribute
-        control_widget = AttributeDeviceDisplayWidget(
-            device=self.external_device_attribute[0],
-            attribute=self.external_device_attribute[1],
-        )
-        self.widget_holder.layout().insertWidget(3, control_widget)
+        if self.device is not None:
+            self.device.attach_attribute_callback(
+                attribute=ATTR_EXTERNAL_TRIGGER,
+                callback=self.sig_control_changed.emit,
+                key_filter=VALUE,
+            )
+
+            # define the status of the input field
+            # using the current value of the attribute
+            self.control_changed(self.device.get_value(ATTR_EXTERNAL_TRIGGER))
+
+            # create the checkbox for the attribute
+            control_widget = AttributeDeviceDisplayWidget(
+                device=self.external_device_attribute[0],
+                attribute=self.external_device_attribute[1],
+            )
+            self.widget_holder.layout().insertWidget(3, control_widget)
 
-        self.set_status_label(self.device.get_value(ATTR_STATUS))
-        self.value_controls = (self.input_value,)
+            self.set_status_label(self.device.get_value(ATTR_STATUS))
+            self.value_controls = (self.input_value,)
 
 
 class DeviceSimpleMethodsListWidget(DeviceMethodWidget):