[gnome-control-center] network: fix a GCC warning

[Cosimo Cecchi <cosimoc src gnome org>]

commit cce521db4a28ac64713f8b0acf5f75172ba5814a
Author: Cosimo Cecchi <cosimo endlessm com>
Date:   Mon Mar 28 16:44:35 2016 -0700

    network: fix a GCC warning
    
    https://bugzilla.gnome.org/show_bug.cgi?id=764296

 .../network/connection-editor/ce-page-security.c   |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/panels/network/connection-editor/ce-page-security.c 
b/panels/network/connection-editor/ce-page-security.c
index ce11e13..80714d5 100644
--- a/panels/network/connection-editor/ce-page-security.c
+++ b/panels/network/connection-editor/ce-page-security.c
@@ -421,7 +421,7 @@ validate (CEPage        *page,
         }
 
         sc = nm_connection_get_setting_connection (connection);
-        firewall_ui_to_setting (sc, CE_PAGE_SECURITY (page)->firewall_combo);
+        firewall_ui_to_setting (sc, GTK_WIDGET (CE_PAGE_SECURITY (page)->firewall_combo));
 
         return valid;
 }