add get_htdocs_dirs

[rupert thurner]

to avoid Trac detected an internal error: AttributeError: 'CustomSelectPanel' object has no attribute 'get_htdocs_dirs'

see ​http://groups.google.com/group/trac-users/browse_thread/thread/f97000ba4331954e

pls add

#text/diff
Index: CustomSelectAdmin/customselectadmin.py
===================================================================
--- CustomSelectAdmin/customselectadmin.py      (revision 6310)
+++ CustomSelectAdmin/customselectadmin.py      (working copy)
@@ -103,6 +103,8 @@
         return 'custom_select_enums.html', data

     # ITemplateProvider methods
+    def get_htdocs_dirs(self):
+        return []
     def get_templates_dirs(self):
         from pkg_resources import resource_filename
         return [resource_filename(__name__, 'templates')]