Adding an profile picture as a background image for a skin causes errors

[Son Nguyen]

Version: master, 1.8

Adding an profile picture as a background image for a skin causes errors:

[WAR] ef (artefact/lib.php:177) Artefact type mismatch. You are trying to use this profileicon as a image.
Call stack (most recent first):

    ArtefactType->__construct(35, null) at /home/sonn/code/mahara/1.8/htdocs/artefact/file/lib.php:293
    ArtefactTypeFileBase->__construct(35, null) at /home/sonn/code/mahara/1.8/htdocs/artefact/file/lib.php:824
    ArtefactTypeFile->__construct(35, null) at /home/sonn/code/mahara/1.8/htdocs/artefact/file/lib.php:1865
    ArtefactTypeImage->__construct(35) at /home/sonn/code/mahara/1.8/htdocs/lib/skin.php:929
    Skin::generate_thumbnail(1) at /home/sonn/code/mahara/1.8/htdocs/lib/skin.php:284
    Skin->commit() at /home/sonn/code/mahara/1.8/htdocs/lib/skin.php:188
    Skin::create(array(size 5)) at /home/sonn/code/mahara/1.8/htdocs/skin/design.php:660
    designskinform_submit(object(Pieform), array(size 44)) at Unknown:0
    call_user_func_array("designskinform_submit", array(size 2)) at /home/sonn/code/mahara/1.8/htdocs/lib/pieforms/pieform.php:528
    Pieform->__construct(array(size 8)) at /home/sonn/code/mahara/1.8/htdocs/lib/pieforms/pieform.php:170
    Pieform::process(array(size 8)) at /home/sonn/code/mahara/1.8/htdocs/lib/pieforms/pieform.php:71
    pieform(array(size 8)) at /home/sonn/code/mahara/1.8/htdocs/skin/design.php:564

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/3105