Tomaz found a bug while attempting to use a workshop module on a recently upgraded site:

Debug info: Argument 4 passed to workshop_extend_navigation() must be an instance of stdClass, instance of cm_info given, called in /html/lib/navigationlib.php on line 1529 and defined
Stack trace:

   * line 351 of /lib/setuplib.php: coding_exception thrown
   * line 1310 of /mod/workshop/lib.php: call to default_error_handler()
   * line 1529 of /lib/navigationlib.php: call to workshop_extend_navigation()
   * line 1056 of /lib/navigationlib.php: call to global_navigation->load_activity()
   * line 2345 of /lib/navigationlib.php: call to global_navigation->initialise()
   * line 641 of /lib/pagelib.php: call to navbar->has_items()
   * line 4 of /theme/arialist/layout/general.php: call to moodle_page->has_navbar()
   * line 647 of /lib/outputrenderers.php: call to include()
   * line 605 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()
   * line ? of unknownfile: call to core_renderer->header()
   * line 189 of /lib/outputrenderers.php: call to call_user_func_array()
   * line ? of unknownfile: call to plugin_renderer_base->__call()
   * line 67 of /mod/workshop/view.php: call to mod_workshop_renderer->header()

The problem is because workshop_extend_navigation is type hinting $cm as a stdClass, and it recently changed to a cm_info object.

I'll create a patch for this shortly.

Cheers
Sam