[gtk/matthiasc/for-master] wayland: Avoid criticals when unsetting transient parents

[Matthias Clasen <matthiasc src gnome org>]

commit 754d6d1a049637c62299cb614065eacc2d17eb45
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Apr 12 12:10:18 2020 -0400

    wayland: Avoid criticals when unsetting transient parents
    
    Must not check the display when parent is NULL.

 gdk/wayland/gdksurface-wayland.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gdk/wayland/gdksurface-wayland.c b/gdk/wayland/gdksurface-wayland.c
index 4269ce97a8..06de4fa500 100644
--- a/gdk/wayland/gdksurface-wayland.c
+++ b/gdk/wayland/gdksurface-wayland.c
@@ -3359,8 +3359,8 @@ gdk_wayland_toplevel_set_transient_for (GdkWaylandToplevel *toplevel,
                                         GdkSurface         *parent)
 {
   g_return_if_fail (!parent || GDK_IS_WAYLAND_TOPLEVEL (parent));
-  g_return_if_fail (gdk_surface_get_display (GDK_SURFACE (toplevel)) ==
-                    gdk_surface_get_display (parent));
+  g_return_if_fail (!parent ||
+                    gdk_surface_get_display (GDK_SURFACE (toplevel)) == gdk_surface_get_display (parent));
 
   if (parent)
     {