No comma betwen journal name and journal number

No comma betwen journal name and journal number

De Gruyter requires no comma between journal name and journal number. So
rather than
Bird, Steven, and Klein, Ewan 1994 Phonological analysis in typed feature
systems. Computational Linguistics, 20 3: 455–491.
they want:
Bird, Steven, and Klein, Ewan 1994 Phonological analysis in typed feature
systems. Computational Linguistics 20 3: 455–491.
I looked at the .bst file I have and found that there is an output.nonull
that probably is responsible for the comma, but I do not know how to
influence it.
\documentclass{article}
\usepackage{filecontents}
\usepackage{natbib}
\begin{filecontents}{SM.bib}
@article{a, author={Max Meier}, title={My first paper}, journal={Journal
of Googelology},
volume=3123, number=1, pages={3--45}, year=2009}
\end{filecontents}
\begin{document}
\nocite{*}
\bibliographystyle{degruyter-hsk}
\bibliography{SM}
\end{document}
De Gruyter .bst is here: degruyter-hsk.bst