window: do not crash without wl_shell
window: do not crash without wl_shell

Since it is the desktop-shell plugin in the compositor that offers both
wl_shell global interface and wl_shell_surface interface, those are not
available on the tablet-shell plugin.

The tablet-shell client uses the toytoolkit, so toytoolkit must work
somehow even without wl_shell.

Turn all operations in toytoolkit that would require wl_shell or
wl_shell_surface into no-ops.

Signed-off-by: Pekka Paalanen <6c0263d81461c956d504307112a4ce25eaacc3d1@gmail.com>

krezovic/weston,Gnurou/weston,kwm81/weston,krezovic/weston,udoprog/weston,Tarnyko/weston-xdg_surface_present,Tarnyko/weston-xdg_surface_present,Fantu/compositor-spice,eyolfson/weston,mchalupa/weston,giucam/weston,jonnylamb/weston,jonnylamb/weston,kwm81/weston,eyolfson/weston,Gnurou/weston,sir-murray/weston,xorgy/weston,sir-murray/weston,Fantu/compositor-spice,xorgy/weston,mchalupa/weston,udoprog/weston,giucam/weston,Fantu/compositor-spice