can't write results file

[hboetes]

Whilst running dr14_tmeter . I run into:

Traceback (most recent call last):
  File "/usr/local/bin/dr14_tmeter", line 26, in <module>
    dr14tmeter.dr14_tmeter.main()
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/dr14_tmeter.py", line 166, in main
    (success, clock, r) = scan_dir_list(subdirlist, options, out_dir)
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/dr14_utils.py", line 87, in scan_dir_list
    write_results(dr, options, out_dir, cur_dir)
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/dr14_utils.py", line 161, in write_results
    append=options.append, dr_database=options.dr_database)
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/dynamic_range_meter.py", line 146, in fwrite_dr
    self.table_txt = wr.write_dr(self, tm)
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/write_dr.py", line 183, in write_dr
    tm.append_separator_line()
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/table.py", line 189, in append_separator_line
    ["----------------------------------------------------------------------------------------------"])
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/table.py", line 110, in append_row
    self.end_row()
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/table.py", line 211, in end_row
    self._append_txt(self.nl())
  File "/usr/local/lib/python3.7/site-packages/dr14tmeter/table.py", line 63, in _append_txt
    self.__txt += txt
TypeError: can only concatenate str (not "NoneType") to str
Time: 0h:01m:11s