allow various calls without keyboard & styling

previously an exception was raised, one of many examples --

  File "blessed/terminal.py", line 492, in wrap
    if line.strip() else ('',))
  File "..lib/python3.3/textwrap.py", line 296, in wrap
    return self._wrap_chunks(chunks)
  File "blessed/sequences.py", line 315, in _wrap_chunks
    Sequence(chunks[-1], term).strip() == '' and lines):
  File "blessed/sequences.py", line 409, in strip
    return self.strip_seqs().strip()
  File "blessed/sequences.py", line 436, in strip_seqs
    nxt = idx + measure_length(self[idx:], self._term)
  File "blessed/sequences.py", line 468, in measure_length
    term._re_will_move.match(ucs) or
AttributeError: 'NullCallableString' object has no attribute 'match'