Invalid get_string() identifier: 'assign:addinstance' or component 'mod_assign'. Perhaps you are missing $string['assign:addinstance'] = ''; in mod/assign/lang/en/assign.php?

line 6510 of /lib/moodlelib.php: call to debugging()

line 7134 of /lib/moodlelib.php: call to core_string_manager->get_string()

line 2770 of /lib/accesslib.php: call to get_string()

line 92 of /admin/webservice/forms.php: call to get_capability_string()

line 166 of /lib/formslib.php: call to external_service_form->definition()

line 66 of /admin/webservice/service.php: call to moodleform->moodleform()