layer-shell: ignore unmapped layer-shell view commits without output (#1023)
layer-shell: ignore unmapped layer-shell view commits without output (#1023)

Fixes #908

This can happen if an output is plugged in and unplugged immediately
(possibly on the noop output): the compositor will close the (unmapped)
layer-surface, it may commit before receiving the close request, but its
output is set to `nullptr` by output-layout (since the output was
destroyed).
ammen99/wayfire,ammen99/wayfire