A PageTool or ContentTool can received the focus when it comes to be deleted. The selection changed message failed because the JCR item does not exist anymore
The solution can be :
- to do not fire selection changed event if a deleted content or deleted page receive the focus ?
or - to catch exception in PageMessageTargetFactory ?
or - to test the existence of the content/page before sending message ?
or - ??
ContentTool must be closed on deletion as PageTool