[gnome-control-center] network: Handle case where GtkComboBox has no active iter

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 4897c6d8e3d35d50074e90fb1953728cb3680cb7
Author: Robert Ancell <robert ancell canonical com>
Date:   Tue Dec 3 15:43:43 2019 +1300

    network: Handle case where GtkComboBox has no active iter

 panels/network/connection-editor/ce-page-security.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/panels/network/connection-editor/ce-page-security.c 
b/panels/network/connection-editor/ce-page-security.c
index cc4182ff3..b8dc791a7 100644
--- a/panels/network/connection-editor/ce-page-security.c
+++ b/panels/network/connection-editor/ce-page-security.c
@@ -126,7 +126,8 @@ security_combo_get_active (CEPageSecurity *self)
         WirelessSecurity *sec = NULL;
 
         model = gtk_combo_box_get_model (self->security_combo);
-        gtk_combo_box_get_active_iter (self->security_combo, &iter);
+        if (!gtk_combo_box_get_active_iter (self->security_combo, &iter))
+                return NULL;
         gtk_tree_model_get (model, &iter, S_SEC_COLUMN, &sec, -1);
 
         return sec;