How to summarize a text ?

This page did not call $PAGE->set_url(...). Using http://tele-ens.univ-oeb.dz/moodle/mod/chat/view.php?id=80606

line 610 of /lib/pagelib.php: call to debugging()
line 830 of /lib/pagelib.php: call to moodle_page->magic_get_url()
line 1795 of /lib/questionlib.php: call to moodle_page->__get()
line 4551 of /lib/navigationlib.php: call to question_extend_settings_navigation()
line 4158 of /lib/navigationlib.php: call to settings_navigation->load_course_settings()
line 769 of /lib/pagelib.php: call to settings_navigation->initialise()
line 830 of /lib/pagelib.php: call to moodle_page->magic_get_settingsnav()
line 136 of /blocks/settings/block_settings.php: call to moodle_page->__get()
line 336 of /blocks/moodleblock.class.php: call to block_settings->get_content()
line 230 of /blocks/moodleblock.class.php: call to block_base->formatted_contents()
line 1181 of /lib/blocklib.php: call to block_base->get_content_for_output()
line 1233 of /lib/blocklib.php: call to block_manager->create_block_contents()
line 643 of /lib/outputrenderers.php: call to block_manager->ensure_content_created()
line 83 of /theme/adaptable/layout/includes/head.php: call to core_renderer->standard_head_html()
line 130 of /theme/adaptable/layout/includes/header.php: call to require_once()
line 30 of /theme/adaptable/layout/columns2.php: call to require_once()
line 1374 of /lib/outputrenderers.php: call to include()
line 1304 of /lib/outputrenderers.php: call to core_renderer->render_page_layout()
line 1941 of /lib/setuplib.php: call to core_renderer->header()
line 64 of /mod/chat/view.php: call to bootstrap_renderer->__call()