desktop-shell: Raise new windows over fullscreen apps

Fixes: https://bugs.freedesktop.org/show_bug.cgi?id=74219
diff --git a/desktop-shell/shell.c b/desktop-shell/shell.c
index e4c0295..690a3be 100644
--- a/desktop-shell/shell.c
+++ b/desktop-shell/shell.c
@@ -4420,6 +4420,8 @@
 	struct weston_surface *old_es;
 	struct shell_surface *shsurf;
 
+	lower_fullscreen_layer(shell);
+
 	main_surface = weston_surface_get_main_surface(es);
 
 	weston_surface_activate(es, seat);