Very minor non-urgent bug

[Henri Salo]

.btc 1

[2013-11-19 13:52:39,658][ERROR    ][bot            ]  ERROR [Failure instance: Traceback: <type 'exceptions.AttributeError'>: 'NoneType' object has no attribute 'expandtabs'
/usr/lib/python2.6/threading.py:504:__bootstrap
/usr/lib/python2.6/threading.py:532:__bootstrap_inner
/usr/lib/python2.6/threading.py:484:run
--- <exception caught here> ---
/home/users/foo/lib/python2.6/site-packages/twisted/python/threadpool.py:191:_worker
/home/users/foo/lib/python2.6/site-packages/twisted/python/context.py:118:callWithContext
/home/users/foo/lib/python2.6/site-packages/twisted/python/context.py:81:callWithContext
/home/users/foo/pyfibot/modules/module_btc.py:12:command_btc
/home/users/foo/pyfibot/botcore.py:399:say
/usr/lib/python2.6/textwrap.py:317:wrap
/usr/lib/python2.6/textwrap.py:146:_munge_whitespace
] command command_btc error

But should just ignore .btc command's input if it is invalid.