Follow up to Bug 798098 fix

If there are GncMainWindows that have no pages added and Gnucash is
quitted they are not destroyed. This fix checks for windows with no
pages and then does a gtk_widget_destroy on them.

gnucash/gnome-utils/gnc-main-window.c

@@ -924,7 +924,8 @@ gnc_main_window_restore_window (GncMainWindow *window, GncMainWindowSaveData *da
     if (error)
         g_error_free(error);
     g_free(window_group);
-    gtk_widget_show(GTK_WIDGET(window));
+    if (window)
+        gtk_widget_show (GTK_WIDGET(window));
 }
 
 void
@@ -1405,12 +1406,26 @@ gnc_main_window_quit(GncMainWindow *window)
     }
     if (do_shutdown)
     {
-        GList *w;
+        GList *w, *next;
 
-        for (w = active_windows; w; w = g_list_next (w))
+        /* This is not a typical list iteration. There is a possability
+         * that the window maybe removed from the active_windows list so
+         * we have to cache the 'next' pointer before executing any code
+         * in the loop. */
+        for (w = active_windows; w; w = next)
         {
-            window = w->data;
-            window->window_quitting = TRUE; // set window_quitting on all windows
+            GncMainWindowPrivate *priv;
+            GncMainWindow *wind = w->data;
+
+            next = g_list_next (w);
+
+            wind->window_quitting = TRUE; // set window_quitting on all windows
+
+            priv = GNC_MAIN_WINDOW_GET_PRIVATE(wind);
+
+            // if there are no pages destroy window
+            if (priv->installed_pages == NULL)
+                gtk_widget_destroy (GTK_WIDGET(wind));
         }
         /* remove the preference callbacks from the main window */
         gnc_main_window_remove_prefs (window);
@@ -1522,6 +1537,10 @@ gnc_main_window_event_handler (QofInstance *entity,  QofEventId event_type,
         if (gnc_plugin_page_has_book (page, (QofBook *)entity))
             gnc_main_window_close_page (page);
     }
+
+    if (GTK_IS_WIDGET(window) && window->window_quitting)
+        gtk_widget_destroy (GTK_WIDGET(window));
+
     LEAVE(" ");
 }
 
@@ -3322,14 +3341,9 @@ gnc_main_window_close_page (GncPluginPage *page)
 
             /* remove the preference callbacks from the main window */
             gnc_main_window_remove_prefs (window);
-
-            gtk_widget_destroy (GTK_WIDGET(window));
-            window = NULL;
         }
         if (window && g_list_length (active_windows) > 1)
-        {
             gtk_widget_destroy (GTK_WIDGET(window));
-        }
     }
 }