Loosen assertion that failed due to a file that ends with #.

Tickled by a freebsd file parsed by 'test/wild.sh all'.

bin/oil.py

@@ -345,6 +345,7 @@ def OshMain(argv, login_shell):
      # TODO: Remove this older form of error handling.
      if not node:
        err = c_parser.Error()
        assert err, err  # can't be empty
        ui.PrintErrorStack(err, arena, sys.stderr)
        return 2  # parse error is code 2

osh/word_parse.py

@@ -1154,16 +1154,20 @@ def _ReadWord(self, lex_mode):
      if self.token_type == Id.Lit_Pound:
        self._Next(lex_mode_e.COMMENT)
        self._Peek()
        assert self.token_type == Id.Ignored_Comment, self.cur_token
        # The next iteration will go into Kind.Ignored and set lex state
        # to lex_mode_e.OUTER/etc.

        # NOTE: The # could be the last character in the file.  It can't be
        # Eof_{RParen,Backtick} because #) and #` are comments.
        assert self.token_type in (Id.Ignored_Comment, Id.Eof_Real), self.cur_token

        # The next iteration will go into Kind.Ignored and set lex state to
        # lex_mode_e.OUTER/etc.
        return None, True  # tell Read() to try again after comment

      else:
        w = self._ReadCompoundWord(lex_mode=lex_mode)
        if not w:
          self.AddErrorContext('Error reading command word',
              token=self.cur_token)
          self.AddErrorContext(
              'Error reading command word', token=self.cur_token)
          return None, False
        return w, False

@@ -1206,7 +1210,7 @@ def ReadWord(self, lex_mode):
      if not need_more:
        break

    if not w:
    if not w:  # Assumes AddErrorContext was already called
      return None

    self.cursor = w