System.InvalidOperationException when selecting a session from the dropdown list that has been closed already

[GoogleCodeExporter]

What steps will reproduce the problem?
- Open three sessions
- In the first one execute "sleep 10 && exit"
- Switch to the second one
- Open the dropdown list with all the opened sessions
- Wait for the first session to close
- When it has closed, select it´s entry from the list

What version of the product are you using? On what operating system?
1.4.0.4 on Windows 7, 64-bit

Please provide any additional information below.
Would need to check if the session is still there when opening it from the 
dropdown list.

Original issue reported on code.google.com by larsen...@web.de on 19 Aug 2014 at 8:01