Chm2pdf fails to process chm's without table of contents

This was reported on https://groups.google.com/forum/#!topic/chm2pdf/SeOGMcMFsBw/discussion

An example of file without toc is in the attchment chmtest_noToc.chm
When trying to convert it by chm2pdf:

chm2pdf --book chmtest_noToc.chm
Traceback (most recent call last):
  File "/usr/local/bin/chm2pdf", line 1156, in <module>
    main(sys.argv)
  File "/usr/local/bin/chm2pdf", line 1150, in main
    convert_to_pdf(cfile, filename, outputfilename, options)
  File "/usr/local/bin/chm2pdf", line 343, in convert_to_pdf
    html_list=get_html_list(cfile)
  File "/usr/local/bin/chm2pdf", line 109, in get_html_list
    lister.feed(topicstree)
  File "/usr/lib/python2.6/sgmllib.py", line 103, in feed
    self.rawdata = self.rawdata + data
TypeError: cannot concatenate 'str' and 'NoneType' objects

A fix has been posted here: lp:~grishkin/chm2pdf/chm2pdf_branch