App crashing on server query cancellation

[keeeeymann]

When I click "find servers" button to fetch Left 4 Dead 2 server list via hl2master.steampowered.com, and then immediately cancel the operation by clicking "stop" (or switching tabs, closing the window), the app throws an error:
System.NullReferenceException: "Reference of object is not pointed to an instance."(My translation)
on ServerBrowser.ServerQueryLogic.Cancel()
...

Confirmed on Windows 7 and Windows 10, both with .Net Framework 4.7 Client profile installed.

Hope it gets fixed, thanks!