Only try and Join a thread if it's not Unstarted

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code/AWB@9396 5227b50d-9349-4574-b055-4b0a7525e11c
Add some ListProvider limits

git-svn-id: svn://svn.code.sf.net/p/autowikibrowser/code/AWB@9397 5227b50d-9349-4574-b055-4b0a7525e11c