[mutter] xwayland: Invert running-as-gdm check

[Jonas Ådahl <jadahl src gnome org>]

commit 0a178a01b345cf8883afcd6ef81274ae20445fb3
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Nov 22 17:59:58 2018 +0100

    xwayland: Invert running-as-gdm check
    
    It was accidentally inverted previously. Lets change it back.

 src/wayland/meta-xwayland.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/wayland/meta-xwayland.c b/src/wayland/meta-xwayland.c
index be29033cf..f0b95351d 100644
--- a/src/wayland/meta-xwayland.c
+++ b/src/wayland/meta-xwayland.c
@@ -388,7 +388,7 @@ choose_xdisplay (MetaXWaylandManager *manager)
 
   if (display_number_override != -1)
     display = display_number_override;
-  else if (!g_getenv ("RUNNING_UNDER_GDM"))
+  else if (g_getenv ("RUNNING_UNDER_GDM"))
     display = 1024;
 
   do