shell: Set input region of the black fullscreen surface

The input region of the black surface placed under the fullscreen shell
surface did not have a specified input region. Because the initial input
region of a surface is infinity, no other surface on any other output
could get any focus.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>

src/shell.c

@@ -1638,6 +1638,8 @@ create_black_surface(struct weston_compositor *ec,
 	weston_surface_set_color(surface, 0.0, 0.0, 0.0, 1);
 	pixman_region32_fini(&surface->opaque);
 	pixman_region32_init_rect(&surface->opaque, 0, 0, w, h);
+	pixman_region32_fini(&surface->input);
+	pixman_region32_init_rect(&surface->input, 0, 0, w, h);
 
 	return surface;
 }