wlr/taskbar not applying empty class

[alexander-zerpa]

Waybar is only applying the empty class to the taskbar when the last window is closed, it also only applies it to the module that had that window icon.

This appears to only be a problem when all-outputs is set to false, so i believe that has something to do with how the taskbar is updated.

I don't know C++ nor have i ever work with GTK but looking at the code my guess is that in the function remove_button on line 880 of the taskbar.cpp file, when you check the tasks_ variable, it will only be empty when there are no more windows open, my instinct would be to use the box_ variable instead but it seems that gtk containers don't keep track of the amount of children they have, so maybe keeping track of that manually would be the path to follow.

When I'm free I will try to implement this and maybe do a pull request but since I'm not very confident on not making a hacky solution I'll leave this Issue here.