[glom] Fix a clang warning.

[Murray Cumming <murrayc src gnome org>]

commit 6a948f1460ad1fc7a41b28787933da8ec4a67f7f
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Nov 15 12:00:56 2013 +0100

    Fix a clang warning.

 glom/frame_glom.cc |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/glom/frame_glom.cc b/glom/frame_glom.cc
index 7386b84..64d6f69 100644
--- a/glom/frame_glom.cc
+++ b/glom/frame_glom.cc
@@ -1607,8 +1607,11 @@ void Frame_Glom::on_menu_developer_relationships_overview()
     Utils::get_glade_widget_derived_with_warning(m_window_relationships_overview);
     add_view(m_window_relationships_overview);
 
-    m_window_relationships_overview->signal_hide().connect( sigc::mem_fun(*this, 
&Frame_Glom::on_developer_dialog_hide));
-    add_window_to_app(m_window_relationships_overview);
+    if(m_window_relationships_overview)
+    {
+      m_window_relationships_overview->signal_hide().connect( sigc::mem_fun(*this, 
&Frame_Glom::on_developer_dialog_hide));
+      add_window_to_app(m_window_relationships_overview);
+    }
   }
 
   if(m_window_relationships_overview)