simple-touch: Attach buffer before posting damage

clients/simple-touch.c

@@ -141,6 +141,7 @@ touch_paint(struct touch *touch, int32_t x, int32_t y, int32_t id)
 	p += touch->width;
 	p[2] = c;
 
+	wl_surface_attach(touch->surface, touch->buffer, 0, 0);
 	wl_surface_damage(touch->surface, x - 2, y - 2, 5, 5);
 	/* todo: We could queue up more damage before committing, if there
 	 * are more input events to handle.