compositor: unmap subsurface views before destroying the subsurfaces

This is to avoid recursing into weston_compositor_build_view_list()
and therefore fix crashing when destroying a stack of visible subsurfaces
due to weston_compositor_build_view_list() being called recursively
and corrupting the lists it works on.

https://bugs.freedesktop.org/show_bug.cgi?id=79684
1 file changed