Strange errors

I think something's wrong with Shared.GetMatchingFileNames(). Maybe a
Linux client issue?
Apparently this can be nil

Strange.
Halt on missing inputItem field

Some people's GUIChats are very messed up. So, we'll abort creating the
chatbox if this is the case and disable the plugin.
Spectator all talk

Spectators can hear both teams voice chat if this is on. They cannot
speak to them however.
Incorrect arguments here

Oops.
Much better method to acquire GUIChat

Also fixes the bug with Medasp's custom HUD mod which would break the
chatbox.
Merge pull request #282 from Person8880/develop

Chatbox fixes