Warning messages while deleting the groups

[Niranjan]

Version: 17:04
Browser: FF, chrome

Steps to rreproduce:

1) Create a group
2)Add a page inside the group
3)Add a text into the page
4)Add a new note into the page and save
5)Now delete the group

Expected result: Page should be deleted without any error
Actual resu;t: Page gets deleted but a warnign message is displayed. see below

Call stack (most recent first):
log_message("call_user_func_array() expects parameter 1 to be a...", 8, true, true, "/home/niranjanbandi/code/mahara/htdocs/lib/mahara....", 1757) at /home/niranjanbandi/code/mahara/htdocs/lib/errors.php:521
error(2, "call_user_func_array() expects parameter 1 to be a...", "/home/niranjanbandi/code/mahara/htdocs/lib/mahara....", 1757, array(size 3)) at /home/niranjanbandi/code/mahara/htdocs/lib/mahara.php:1757
call_static_method("ArtefactTypeHtml", "bulk_delete", array(size 1)) at /home/niranjanbandi/code/mahara/htdocs/artefact/lib.php:763
ArtefactType::delete_by_artefacttype(array(size 1)) at /home/niranjanbandi/code/mahara/htdocs/lib/group.php:801
group_delete(20) at /home/niranjanbandi/code/mahara/htdocs/group/delete.php:54
deletegroup_submit(object(Pieform), array(size 2)) at /home/niranjanbandi/code/mahara/htdocs/lib/pieforms/pieform.php:543
Pieform->__construct(array(size 5)) at /home/niranjanbandi/code/mahara/htdocs/lib/pieforms/pieform.php:164
Pieform::process(array(size 5)) at /home/niranjanbandi/code/mahara/htdocs/lib/mahara.php:4799
pieform(array(size 5)) at /home/niranjanbandi/code/mahara/htdocs/group/delete.php:41

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/7283

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/7283
Committed: https://git.mahara.org/mahara/mahara/commit/310c09fe561affe82f0d967c66b847f07f18d0a7
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit 310c09fe561affe82f0d967c66b847f07f18d0a7
Author: Cecilia Vela Gurovic <email address hidden>
Date: Thu Dec 1 12:52:43 2016 +1300

Bug 1646284: Deleting a group with warnings artefact/html

behatnotneeded

Change-Id: Iaf0615385534478872a11ffe22fb374ca689ad06