get_role_users() without specifying one single roleid needs to be called prefixing role assignments id (ra.id) as unique field, you can use $fields param for it.
line 4079 of /public/lib/accesslib.php: call to debugging()
line 414 of /public/theme/mb2nl/renderers/core_course.php: call to get_role_users()
line 258 of /public/theme/mb2nl/renderers/core_course.php: call to theme_mb2nl_core_course_renderer->coursecat_coursebox_content()
line 86 of /public/course/renderer.php: call to theme_mb2nl_core_course_renderer->coursecat_coursebox()
line 76 of /public/course/info.php: call to core_course_renderer->course_info_box()
