Determine which groups to Hide correctly
Determine which groups to Hide correctly

This is a fix I have applied locally to make sure that when I use decorated layouts like tabbed in groups, XMonad does not leave bogus decoration windows lying around.

I think that the issue fixed is that the set of groups to send `Hide` to is determined by subtracting the extant groups from `l`, but `l` has already been put through `readapt` and so some groups may have been removed (if they are empty), so they don't get the Hide message.

The comparison should therefore be between `_l` and the new groups.
xmonad/xmonad-contrib,xmonad/xmonad-contrib,f1u77y/xmonad-contrib,f1u77y/xmonad-contrib