Patch solved the problem for me, did not get a response from submitter in Debian BTS. Please include the changes in next version of tex4ht and close the issue. Thanks!

See http://bugs.debian.org/615596

Calling mk4ht dblatex some_file.tex results in this error:

System call: java -classpath /usr/share/tex4ht/tex4ht.jar xtpipes -i
/usr/share/texmf/tex4ht/xtpipes/ -o some_file.xml some_file.tmp
--- xtpipes error 32 --- Missing 4xt script file name
--- Warning --- System return: 256

This makes it impossible to create docbook files from a LaTeX
source.
Minimal example is below: it turns out that the documenclass are not supported for dblatex output, i.e. there is no entry in docbook.4ht. Please consider to add it.

\documentclass{scrreprt}
\begin{document}
test
\end{document}