shell: Create a view for the grab_surface

Without the view, we can't set pointer and touch focus to the grab_surface
and touch moving fails.
diff --git a/src/shell.c b/src/shell.c
index fdc163e..d29bb89 100644
--- a/src/shell.c
+++ b/src/shell.c
@@ -2815,6 +2815,7 @@
 	struct desktop_shell *shell = wl_resource_get_user_data(resource);
 
 	shell->grab_surface = wl_resource_get_user_data(surface_resource);
+	weston_view_create(shell->grab_surface);
 }
 
 static void