chm2pdf crashes on CHM file

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Running chm2pdf --book <chm file>
2.
3.

What is the expected output? What do you see instead?
Traceback (most recent call last):
  File "/usr/local/bin/chm2pdf", line 887, in <module>
    main(sys.argv)
  File "/usr/local/bin/chm2pdf", line 883, in main
    convert_to_pdf(cfile, filename, outputfilename, options)
  File "/usr/local/bin/chm2pdf", line 179, in convert_to_pdf
    html_list=get_html_list(cfile)
  File "/usr/local/bin/chm2pdf", line 88, in get_html_list
    lister.feed(topicstree)
  File "/usr/lib/python2.7/sgmllib.py", line 103, in feed
    self.rawdata = self.rawdata + data
TypeError: cannot concatenate 'str' and 'NoneType' objects

What version of the product are you using? On what operating system?
0.9.1-1.1ubuntu4

Please provide any additional information below.
I can provide the CHM file by email. Mail me at harwinder@gmail.com

Original issue reported on code.google.com by harwinde...@utradesolutions.com on 5 Aug 2011 at 5:24

[GoogleCodeExporter]

I can also provide a CHM file which raises the same error: fmota91 at gmail dot 
com. I have also tried the --webpage and --continuous options, with the same 
result.

Original comment by FMot...@gmail.com on 29 Aug 2011 at 7:24