Description of problem:
When will it stop crashing on close?

Version-Release number of selected component:
meld-3.22.0-2.fc38

Additional info:
reporter:       libreport-2.17.11
kernel:         6.3.12-200.fc38.x86_64
cmdline:        /usr/bin/python3 /usr/bin/meld discord-0.0.28-2.spec discord-0.0.28-2.x86_64.spec
cgroup:         0::/user.slice/user-1000.slice/session-4.scope
uid:            0
reason:         settings.py:58:on_setting_changed:AttributeError: 'NoneType' object has no attribute 'props'
executable:     /usr/bin/meld
type:           Python3
package:        meld-3.22.0-2.fc38
runlevel:       N 5
exception_type: AttributeError
crash_function: on_setting_changed
interpreter:    python3-3.11.4-1.fc38.x86_64
comment:        When will it stop crashing on close?

Truncated backtrace:
settings.py:58:on_setting_changed:AttributeError: 'NoneType' object has no attribute 'props'

Traceback (most recent call last):
  File "/usr/bin/meld", line 463, in <module>
    sys.exit(main())
             ^^^^^^
  File "/usr/bin/meld", line 458, in main
    setup_settings()
  File "/usr/bin/meld", line 317, in setup_settings
    meld.settings.create_settings()
  File "/usr/lib/python3.11/site-packages/meld/settings.py", line 124, in create_settings
    _meldsettings = MeldSettings()
                    ^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/site-packages/meld/settings.py", line 39, in __init__
    self.on_setting_changed(settings, 'prefer-dark-theme')
  File "/usr/lib/python3.11/site-packages/meld/settings.py", line 58, in on_setting_changed
    gtk_settings.props.gtk_application_prefer_dark_theme = prefer_dark
    ^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'props'

Local variables in innermost frame:
self: <settings.MeldSettings object at 0x7f6dd43b4ec0 (meld+settings+MeldSettings at 0x559400b94f90)>
settings: <Gio.Settings object at 0x7f6dd43d0840 (GSettings at 0x559400b84970)>
key: 'prefer-dark-theme'
gtk_settings: None
prefer_dark: False