ActionOverflow crashes when there is an ActionSeparator

[yves-surrel]

In example widgets\actionbar.py, if anActionSeparator is added, shrinking the window to have ActionOverflow firing makes the window become black and then Kivy crashes.

from kivy.base import runTouchApp
from kivy.lang import Builder

runTouchApp(Builder.load_string('''
ActionBar:
    pos_hint: {'top':1}
    ActionView:
        use_separator: True
        ActionPrevious:
            title: 'Action Bar'
            with_previous: False
        ActionOverflow:
        ActionButton:
            icon: 'atlas://data/images/defaulttheme/audio-volume-high'
        ActionButton:
            important: True
            text: 'Important'
        ActionButton:
            text: 'Btn2'
        ActionButton:
            text: 'Btn3'
        ActionButton:
            text: 'Btn4'
        ActionSeparator:   # <------------------ Added
        ActionGroup:
            text: 'Group1'
            ActionButton:
                text: 'Btn5'
            ActionButton:
                text: 'Btn6'
            ActionButton:
                text: 'Btn7'
'''))

MacOS, Python v3.9.13, Kivy v2.3.0