keyboard-group: two NULL keymaps are equal
keyboard-group: two NULL keymaps are equal

Previously, creating a keyboard group without any keymap set would
result in an error:

    Device keymap does not match keyboard group's

ascent12/wlroots,SirCmpwn/wlroots,ascent12/wlroots,swaywm/wlroots,swaywm/wlroots