Error when trying to apply settings on the brightness slider tab

[therealmate]

Describe the bug
Can't change any setting on the brightness slider tab (e.g.:changing backend from brightnessctl to ddcutil.)

Traceback (most recent call last):
File "/usr/lib/python3.13/site-packages/nwg_panel/config.py", line 1305, in restart_panel
self.apply_changes()
~~~~~~~~~~~~~~~~~~^^
File "/usr/lib/python3.13/site-packages/nwg_panel/config.py", line 1285, in apply_changes
self.update_brightness_slider()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
File "/usr/lib/python3.13/site-packages/nwg_panel/config.py", line 3251, in update_brightness_slider
settings[setting] = value
^^^^^
UnboundLocalError: cannot access local variable 'value' where it is not associated with a value

To Reproduce
Steps to reproduce the behavior:

1. Go to Panel settings
2. Click on 'Brightness slider'
3. Click Apply or Apply/restart
4. See error in terminal

Expected behavior
Being able to change settings on the brightness slider tab

Desktop (please complete the following information):

• Distro: Arch Linux
• WM: Labwc
• nwg-panel version: 0.9.58

Additional context
Maybe it could be considered to change the default brightness backend from brightnessctl to ddcutil as ddcutil probably works on more devices (including mine)

[nwg-piotr]

I've added a patch to avoid crashes like this, but generally I'd like to get rid of this module one day. It is difficult to configure and unreliable in operation.