info: handle dialog closing consistently

The 'Other media' dialog is just hidden when the close button is
clicked (so that it can be shown again), but when closing it with
the Escape key, it gets destroyed and an attempt to bring it up
again just shows a sad empty little square.

https://bugzilla.gnome.org/show_bug.cgi?id=659948

panels/info/cc-info-panel.c

@@ -1293,6 +1293,10 @@ on_extra_options_button_clicked (GtkWidget    *button,
                     "response",
                     G_CALLBACK (on_extra_options_dialog_response),
                     self);
+  g_signal_connect (dialog,
+                    "delete-event",
+                    G_CALLBACK (gtk_widget_hide_on_delete),
+                    NULL);
   /* update other_application_combo */
   other_type_combo_box_changed (GTK_COMBO_BOX (combo_box), self);
   gtk_window_present (GTK_WINDOW (dialog));