When certificates is enabled for a course and an admin or instructor tries to run a complete activity report for that user it displays the below error message. This has been reproduced on three different 2.6.3 sites. The 2nd and 3rd tests were on test sites with fresh courses.
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The steps to reproduce are:
1)Create a new course.
2)Add a student.
3)Add a certificate. Default settings are fine.
4)Login as the student and get the certificate.
5)As admin go to the enrolled users. Click on the student to view profile.
6)In "Profile setting for <name of student> select Activity reports / ► Complete report.
7)See error message. Debugging pasted.
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Coding error detected, it must be fixed by a programmer: Invalid database query parameter value

More information about this error

Debug info: Objects are are not allowed: context_module
Error code: codingerror
Stack trace:
line 782 of /lib/dml/moodle_database.php: coding_exception thrown
line 801 of /lib/dml/moodle_database.php: call to moodle_database->detect_objects()
line 991 of /lib/dml/mysqli_native_moodle_database.php: call to moodle_database->fix_sql_params()
line 579 of /lib/filestorage/file_storage.php: call to mysqli_native_moodle_database->get_records_sql()
line 617 of /mod/certificate/lib.php: call to file_storage->get_area_files()
line 213 of /mod/certificate/lib.php: call to certificate_print_user_files()
line 129 of /report/outline/user.php: call to certificate_user_complete()