Running \words on someone without words in the db crashes it

[Lorenz Leitner]

/usr/lib/python3/dist-packages/sklearn/externals/joblib.py:1: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
  import imp
Exception in thread Thread-2:
Traceback (most recent call last):
  File "/usr/lib/python3.7/threading.py", line 917, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.7/threading.py", line 865, in run
    self._target(*self._args, **self._kwargs)
  File "/home/pi/git/ircbot/ircbot.py", line 246, in receive_and_parse_msg_loop
    self.receive_and_parse_msg()
  File "/home/pi/git/ircbot/ircbot.py", line 251, in receive_and_parse_msg
    self.receive_and_parse_irc_msg(ircmsg)
  File "/home/pi/git/ircbot/ircbot.py", line 313, in receive_and_parse_irc_msg
    self.execute_command(name, message)
  File "/home/pi/git/ircbot/ircbot.py", line 382, in execute_command
    self.commands_[command_name].execute([name, message])
  File "/home/pi/git/ircbot/command.py", line 247, in execute
    bow = cv.fit_transform(msgs)
  File "/usr/lib/python3/dist-packages/sklearn/feature_extraction/text.py", line 1032, in fit_transform
    self.fixed_vocabulary_)
  File "/usr/lib/python3/dist-packages/sklearn/feature_extraction/text.py", line 961, in _count_vocab
    raise ValueError("empty vocabulary; perhaps the documents only"
ValueError: empty vocabulary; perhaps the documents only contain stop words