[gdl] Fix NULL-instance error when emitting signal

[Johannes Schmid <jhs src gnome org>]

commit c78ed8047debf90f5439c30de82e4fd27150d804
Author: Johannes Schmid <jhs gnome org>
Date:   Sun Jul 22 14:44:06 2012 +0200

    Fix NULL-instance error when emitting signal

 gdl/gdl-dock-object.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gdl/gdl-dock-object.c b/gdl/gdl-dock-object.c
index f5c5190..dcc319a 100644
--- a/gdl/gdl-dock-object.c
+++ b/gdl/gdl-dock-object.c
@@ -398,7 +398,8 @@ gdl_dock_object_update_parent_visibility (GdlDockObject *object)
                                &visible);
         gtk_widget_set_visible (GTK_WIDGET (parent), visible);
     }
-    g_signal_emit_by_name (GDL_DOCK_OBJECT (object)->master, "layout-changed");
+    if (object->master)
+        g_signal_emit_by_name (object->master, "layout-changed");
 }
 
 static void