[gnome-initial-setup] gis-assistant: Handle a NULL current_page properly

[Jasper St. Pierre <jstpierre src gnome org>]

commit a745c9cc35a114468b959aad7181f3967d0d78a3
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Tue Aug 21 15:33:49 2012 -0400

    gis-assistant: Handle a NULL current_page properly

 gnome-initial-setup/gis-assistant.c |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)
---
diff --git a/gnome-initial-setup/gis-assistant.c b/gnome-initial-setup/gis-assistant.c
index 4c2a27c..cae83be 100644
--- a/gnome-initial-setup/gis-assistant.c
+++ b/gnome-initial-setup/gis-assistant.c
@@ -134,7 +134,11 @@ void
 gis_assistant_next_page (GisAssistant *assistant)
 {
   GisAssistantPrivate *priv = assistant->priv;
-  PageData *next_page = (PageData *) priv->current_page->link->next->data;
+  PageData *next_page;
+
+  g_return_if_fail (priv->current_page != NULL);
+
+  next_page = (PageData *) priv->current_page->link->next->data;
   gis_assistant_switch_to (assistant, next_page->widget);
 }
 
@@ -142,7 +146,11 @@ void
 gis_assistant_previous_page (GisAssistant *assistant)
 {
   GisAssistantPrivate *priv = assistant->priv;
-  PageData *prev_page = (PageData *) priv->current_page->link->prev->data;
+  PageData *prev_page;
+
+  g_return_if_fail (priv->current_page != NULL);
+
+  prev_page = (PageData *) priv->current_page->link->prev->data;
   gis_assistant_switch_to (assistant, prev_page->widget);
 }
 
@@ -154,6 +162,9 @@ update_navigation_buttons (GisAssistant *assistant,
   PageData *current_page = priv->current_page;
   gboolean can_go_backward, can_go_forward, is_last_page;
 
+  if (current_page == NULL)
+    return;
+
   can_go_backward = (current_page->link->prev != NULL);
   gtk_widget_set_sensitive (priv->back, can_go_backward);
 
@@ -282,7 +293,10 @@ gchar *
 gis_assistant_get_title (GisAssistant *assistant)
 {
   GisAssistantPrivate *priv = assistant->priv;
-  return priv->current_page->title;
+  if (priv->current_page != NULL && priv->current_page->title != NULL)
+    return priv->current_page->title;
+  else
+    return "";
 }
 
 GtkWidget *