[mutter] display: Don't grab transient's parent unconditionally

[Florian Müllner <fmuellner src gnome org>]

commit a6601e92aa12a0e8a2091a0837b50a1240b767e7
Author: Florian Müllner <fmuellner gnome org>
Date:   Fri May 2 12:20:32 2014 +0200

    display: Don't grab transient's parent unconditionally
    
    Since commit 6e8d1d79d, move operations are always performed for
    the (toplevel) parent of all transient, which is just plain silly
    if the dialog is not actually attached to its parent (either because
    the dialog is not modal or the setting is disabled).

 src/core/display.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/core/display.c b/src/core/display.c
index 1c6b9c0..a08c8f9 100644
--- a/src/core/display.c
+++ b/src/core/display.c
@@ -1773,7 +1773,8 @@ meta_display_begin_grab_op (MetaDisplay *display,
   /* If window is a modal dialog attached to its parent,
    * grab the parent instead for moving.
    */
-  if (meta_grab_op_is_moving (op))
+  if (window && meta_window_is_attached_dialog (window) &&
+      meta_grab_op_is_moving (op))
     grab_window = get_toplevel_transient_for (window);
 
   g_assert (grab_window != NULL);