input: Keep track of number of touch points inside touch struct

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
diff --git a/src/shell.c b/src/shell.c
index dfcb525..00e0f1c 100644
--- a/src/shell.c
+++ b/src/shell.c
@@ -1457,7 +1457,7 @@
 		(struct weston_touch_move_grab *) container_of(
 			grab, struct shell_touch_grab, grab);
 
-	if (grab->touch->seat->num_tp == 0) {
+	if (grab->touch->num_tp == 0) {
 		shell_touch_grab_end(&move->base);
 		free(move);
 	}