seat: unhide the cursor if it is warped to focus

Unhide the cursor if container warping is enabled.
Also set the image_surface to NULL during view_unmap, otherwise the cursor will
try to access the surface which is currently being unmapped.

sway/input/seat.c

@@ -1231,4 +1231,8 @@ void seat_consider_warp_to_focus(struct sway_seat *seat) {
 	} else {
 		cursor_warp_to_workspace(seat->cursor, focus->sway_workspace);
 	}
+	if (seat->cursor->hidden){
+		cursor_unhide(seat->cursor);
+		wl_event_source_timer_update(seat->cursor->hide_source, cursor_get_timeout(seat->cursor));
+	}
 }

sway/tree/view.c

@@ -654,6 +654,7 @@ void view_unmap(struct sway_view *view) {
 
 	struct sway_seat *seat;
 	wl_list_for_each(seat, &server.input->seats, link) {
+		seat->cursor->image_surface = NULL;
 		seat_consider_warp_to_focus(seat);
 	}