Problems with Image Occlusion Enhanced Add-On

Hey everyone,
I have a problem with my Image Occlusion Enhanced Add-on with the desktop version of anki.
An error warning occurs when i want to add the cards to my deck with th “hide all, guess one” button.
Did anyone have that same error? And how did you solve it?
I am afraid, if I am deleting the add-on and downloading it back again, all my cards will be lost.
The last days, and even this morning, everything worked perfectly fine and from one moment to another that problem occured.

This is the Debuginformation I got (if that helps somehow):

Anki 2.1.48 (fb07bad3) Python 3.8.6 Qt 5.14.2 PyQt 5.14.2
Platform: Windows 10
Flags: frz=True ao=True sv=2
Add-ons, last update check: 2021-10-25 08:30:28

Caught exception:
Traceback (most recent call last):
File “aqt\”, line 541, in handler
File “C:\Users\pauli\AppData\Roaming\Anki2\addons21\1374772155\”, line 278, in
lambda val, choice=choice, close=close: self._onAddNotesButton(choice, close, val))
File “C:\Users\pauli\AppData\Roaming\Anki2\addons21\1374772155\”, line 293, in _onAddNotesButton
r = gen.generateNotes()
File “C:\Users\pauli\AppData\Roaming\Anki2\addons21\1374772155\”, line 80, in generateNotes
(svg_node, layer_node) = self._getMnodesAndSetIds()
File “C:\Users\pauli\AppData\Roaming\Anki2\addons21\1374772155\”, line 190, in _getMnodesAndSetIds
mask_doc = minidom.parseString(self.new_svg.encode(‘utf-8’))
AttributeError: ‘NoneType’ object has no attribute ‘encode’