extension selection is empty if item id has invalid value

Summary:

As you can see the item is selected in in canvas, but if i want to process it by python extension self.svg.selected will be None. This is definetely a bug. Even if id is strange the selection should reflect proper items.

Steps to reproduce:

1. Open Inkscape
2. Create a rectangle
3. remove all attributes except "id" of the default created default layer1 which contains that rectangle.
4. Edit the value of the id and set it to "#000000;". If other attributes like inkscape:label exist the bug does not occur
5. Run a python extension

What happened?

• self.svg.selected is None while it is not none in visual GUI selection

What should have happened?

• Item should still be selected in the code backend.

Version Info:

• Inkscape version: Inkscape 1.2-dev (1:1.0+devel+202104121159+inkscape@efe07b5b)