Keyword URLs for Drupal6 are broken with GeSHi library 1.0.8.4

When Keyword URLs are enabled, these urls for Drupal language blocks are broken.
E.g. the input

[code lang="drupal6"]
form_set_error('thingy', 'ur doin it rong');
[/code]

gives something like

<a href="http://api.drupal.org/api/function/form_set_error/<span class="nu0">6"><span class="kw5">form_set_error</span></a><span class="br0">&#40;</span><span class="st0">'thingy'</span>, <span class="st0">'ur doin it rong'</span><span class="br0">&#41;</span>;

The "6" in the url apparently triggers some extra filtering in the GeSHi library and breaks the url.

GeSHi version 1.0.8.3 and probably before are fine, 1.0.8.4 has the problem.

This is a bug/problem in the GeSHi library, discussed at http://sourceforge.net/tracker/index.php?func=detail&atid=670231&aid=280...