[gnome-control-center] network: Fix warning when opening IPv4 connection editor

[Bastien Nocera <hadess src gnome org>]

commit da7be92093be4be359b33fd0dd3788c41ff89e4e
Author: Bastien Nocera <hadess hadess net>
Date:   Fri Sep 16 16:50:15 2016 +0200

    network: Fix warning when opening IPv4 connection editor
    
    https://bugzilla.gnome.org/show_bug.cgi?id=771515

 panels/network/connection-editor/ce-page-ip4.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/panels/network/connection-editor/ce-page-ip4.c b/panels/network/connection-editor/ce-page-ip4.c
index 51995f9..f747f39 100644
--- a/panels/network/connection-editor/ce-page-ip4.c
+++ b/panels/network/connection-editor/ce-page-ip4.c
@@ -209,7 +209,7 @@ add_address_row (CEPageIP4   *page,
         gtk_label_set_mnemonic_widget (GTK_LABEL (label), widget);
         g_signal_connect_swapped (widget, "changed", G_CALLBACK (ce_page_changed), page);
         g_object_set_data (G_OBJECT (row), "gateway", widget);
-        gtk_entry_set_text (GTK_ENTRY (widget), gateway);
+        gtk_entry_set_text (GTK_ENTRY (widget), gateway ? gateway : "");
         gtk_widget_set_margin_start (widget, 10);
         gtk_widget_set_margin_end (widget, 10);
         gtk_widget_set_hexpand (widget, TRUE);