view: remove pointer constraints on unmap

If the view has any pointer constraints, ensure they are removed
before the view is unmapped and the surface is no longer tied to the
view.

sway/tree/view.c

@@ -664,6 +664,13 @@ 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;
+		if (seat->cursor->active_constraint) {
+			struct wlr_surface *constrain_surface =
+				seat->cursor->active_constraint->surface;
+			if (view_from_wlr_surface(constrain_surface) == view) {
+				sway_cursor_constrain(seat->cursor, NULL);
+			}
+		}
 		seat_consider_warp_to_focus(seat);
 	}