Please see MDL-24034 for steps to reproduce the following error message:

Coding problem: this page does not set $PAGE->context properly.

• line 337 of /lib/pagelib.php: call to debugging()
• line 594 of /lib/pagelib.php: call to moodle_page->magic_get_context()
• line 1221 of /lib/weblib.php: call to moodle_page->__get()
• line 136 of /mod/assignment/lib.php: call to format_string()
• line 39 of /mod/assignment/type/upload/assignment.class.php: call to assignment_base->assignment_base()
• line 68 of /mod/assignment/locallib.php: call to assignment_upload->assignment_upload()
• line 189 of /portfolio/add.php: call to assignment_portfolio_caller->load_data()

Notice: Trying to get property of non-object in /var/www/head/moodle/mod/assignment/locallib.php on line 80