b=715063 don't warn when org.gnome.system.proxy GSettings schemas are not found r=roc

--HG--
extra : rebase_source : 99fa820e3513bd8355a3bfee00f0020bb5a3ef4a

toolkit/system/unixproxy/nsUnixSystemProxySettings.cpp

@@ -456,7 +456,8 @@ nsUnixSystemProxySettings::GetProxyFromGSettings(const nsACString& aScheme,
 
   rv = mGSettings->GetCollectionForSchema(NS_LITERAL_CSTRING("org.gnome.system.proxy"),
                                           getter_AddRefs(proxy_settings));
-  NS_ENSURE_SUCCESS(rv, rv);
+  if (NS_FAILED(rv))
+    return rv;
 
   nsCString proxyMode; 
   rv = proxy_settings->GetString(NS_LITERAL_CSTRING("mode"), proxyMode);