title: word_tokenize in nltk not taking a list of string as argument
body: <pre><code>from nltk.tokenize import word_tokenize
  
  music_comments = [['So cant you just run the bot outside of the US? ', ''], ["Just because it's illegal doesn't mean it will stop. I hope it actually gets enforced. ", ''], ['Can they do something about all the fucking bots on Tinder next?   \n\nEdit: Holy crap my inbox just blew up ', '']]
  
  print(word_tokenize(music_comments[1]))
  </code></pre>
  
  <p>I found <a href="https://stackoverflow.com/questions/33773157/word-tokenize-typeerror-expected-string-or-buffer">this other question</a> which says to pass a list of strings to word_tokenize, but in my case after running the above I get the following output:</p>
  
  <pre><code>Traceback (most recent call last):
    File "testing.py", line 5, in &lt;module&gt;
      print(word_tokenize(music_comments[1]))
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\__init__.py", line 109, in word_tokenize
      return [token for sent in sent_tokenize(text, language)
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\__init__.py", line 94, in sent_tokenize
      return tokenizer.tokenize(text)
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\punkt.py", line 1237, in tokenize
      return list(self.sentences_from_text(text, realign_boundaries))
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\punkt.py", line 1285, in sentences_from_text
      return [text[s:e] for s, e in self.span_tokenize(text, realign_boundaries)]
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\punkt.py", line 1276, in span_tokenize
      return [(sl.start, sl.stop) for sl in slices]
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\punkt.py", line 1276, in &lt;listcomp&gt;
      return [(sl.start, sl.stop) for sl in slices]
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\punkt.py", line 1316, in _realign_boundaries
      for sl1, sl2 in _pair_iter(slices):
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\punkt.py", line 310, in _pair_iter
      prev = next(it)
    File "C:\Users\Shraddheya Shendre\Anaconda3\lib\site-packages\nltk\tokenize\punkt.py", line 1289, in _slices_from_text
      for match in self._lang_vars.period_context_re().finditer(text):
  TypeError: expected string or bytes-like object
  </code></pre>
  
  <p>What is the problem? What am I missing?</p>