shell: Fix crash when restoring focus state during workspace change
shell: Fix crash when restoring focus state during workspace change

The check to avoid calling weston_keyboard_set_focus() for a seat that
didn't have a keyboard in restore_focus_state() was cheking the wrong
seat (the one from the previous loop). That caused a crash when
switching workspaces if there was an extra seat that didn't have a
keyboard.

https://bugs.freedesktop.org/show_bug.cgi?id=78349

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