[glom] Dnd layout: Avoid a crash when dragging to empty space.

[Murray Cumming <murrayc src gnome org>]

commit 3a6c4cb509765c4eed5766d914ffc6e754c90c0a
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Dec 30 21:56:53 2009 +0100

     Dnd layout: Avoid a crash when dragging to empty space.
    
    * glom/utility_widgets/flowtable_dnd.cc: on_drag_data_received():
    Avoid dereferencing a null group. Bug #599232

 ChangeLog                             |    7 +++++++
 glom/mode_data/flowtablewithfields.cc |    3 ++-
 glom/utility_widgets/flowtable_dnd.cc |   14 ++++++++------
 3 files changed, 17 insertions(+), 7 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 20e82e3..ff64d44 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2009-12-30  Murray Cumming  <murrayc murrayc com>
 
+  Dnd layout: Avoid a crash when dragging to empty space.
+  
+	* glom/utility_widgets/flowtable_dnd.cc: on_drag_data_received():
+	Avoid dereferencing a null group.
+
+2009-12-30  Murray Cumming  <murrayc murrayc com>
+
 	Dnd layout: Avoid a crash.
 
 	* glom/utility_widgets/flowtable_dnd.cc: on_drag_data_received():
diff --git a/glom/mode_data/flowtablewithfields.cc b/glom/mode_data/flowtablewithfields.cc
index 58d1590..a6f43ff 100644
--- a/glom/mode_data/flowtablewithfields.cc
+++ b/glom/mode_data/flowtablewithfields.cc
@@ -1416,7 +1416,8 @@ void FlowTableWithFields::on_dnd_remove_placeholder()
 
 void FlowTableWithFields::dnd_notify_failed_drop()
 {
-  // TODO: Avoid this error message
+  // TODO: Avoid this error message, maybe by adding a group.
+  // TODO: At least avoid losing the dragged item.
   Gtk::MessageDialog dialog(_("You cannot drop anything here. Try to add a group first"),
                       false, Gtk::MESSAGE_ERROR);
   dialog.run();
diff --git a/glom/utility_widgets/flowtable_dnd.cc b/glom/utility_widgets/flowtable_dnd.cc
index 42fd285..e0dd5bc 100644
--- a/glom/utility_widgets/flowtable_dnd.cc
+++ b/glom/utility_widgets/flowtable_dnd.cc
@@ -208,15 +208,17 @@ void FlowTableDnd::on_drag_data_received(const Glib::RefPtr<Gdk::DragContext>& d
       sharedptr<LayoutItem> item = base->get_layout_item();
       if(item)
       {
+        m_internal_drag = false;
         sharedptr<LayoutGroup> group = sharedptr<LayoutGroup>::cast_dynamic(get_layout_item());
-        LayoutGroup::type_list_items items = group->m_list_items;
-        if(std::find(items.begin(), items.end(), item) != items.end())
+        if(group)
         {
-          m_internal_drag = true;
-          group->remove_item(item);
+          LayoutGroup::type_list_items items = group->m_list_items;
+          if(std::find(items.begin(), items.end(), item) != items.end())
+          {
+            m_internal_drag = true;
+            group->remove_item(item);
+          }
         }
-        else
-          m_internal_drag = false;
 
         LayoutWidgetBase* above_casted = dynamic_cast<LayoutWidgetBase*>(above);
         on_dnd_add_layout_item(above_casted, item);