Preserve behavior of GDM <49.
Fir details, see:
https://github.com/ibus/ibus/commit/c15880007cfaa75f0863189f3a2def9b4f83ea8f

Index: bus/main.c
--- bus/main.c.orig
+++ bus/main.c
@@ -56,7 +56,8 @@ static gchar *config = "default";
 static gchar *desktop = "gnome";
 
 static gchar *panel_extension_disable_users[] = {
-    "gnome-initial-setup",
+    "_gdm",
+    "_gnome-initial-setup",
     "liveuser"
 };
 static gchar *panel_extension_disable_groups[] = {
