Rule reorder buttons in layer stylization throw an error

[gabrimonfa]

Maestro trunk (2011-10-24) OS: Windows XP SP3

In layer stylization if I try to change rules order using the buttons I receive the following error (translated back to english, so wording may be a little different)

System.InvalidCastException: Cannot cast an object of type  '<get_Rules>d__0' into type 'System.Collections.IList'.
   in Maestro.Editors.LayerDefinition.Vector.Scales.ConditionList.MoveSelectedRule(Boolean down) in z:\maestro_src\Maestro.Editors\LayerDefinition\Vector\Scales\ConditionList.cs:riga 322
   in Maestro.Editors.LayerDefinition.Vector.Scales.ConditionListButtons.MoveRuleDownButton_Click(Object sender, EventArgs e) in z:\maestro_src\Maestro.Editors\LayerDefinition\Vector\Scales\ConditionListButtons.cs:riga 253
   in System.Windows.Forms.Control.OnClick(EventArgs e)
   in System.Windows.Forms.Button.OnClick(EventArgs e)
   in System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   in System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   in System.Windows.Forms.Control.WndProc(Message& m)
   in System.Windows.Forms.ButtonBase.WndProc(Message& m)
   in System.Windows.Forms.Button.WndProc(Message& m)
   in System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   in System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   in System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

What is bad of this bug is that UI does swap rules so user think that despite the error the reorder succeeded.

Then obviously layer stylization is different than expected looking at the UI.

[jng]

Fixed r6182