Fatal error trying to copy a page with "journal" block

This is another bug caused by the performance patch that auto-loaded htdocs/artefact/lib.php into every single page load.

To replicate:

1. Create a journal with a journal entry.
2. Put a "journal" block in a page, with that journal selected.
3. Set the journal block's copying settings to "They get a copy of my journal"
4. Make the page copyable by other users and share it with other users
5. Log in as another user
6. Try to copy that page

Expected result: You get a copy of the page
Actual result: You see a fatal error.

( ! ) Fatal error: Call to undefined function artefact_get_descendants() in /home/aaronw/www/mahara/htdocs/blocktype/lib.php on line 1548
Call Stack
# Time Memory Function Location
1 0.0001 252504 {main}( ) ../copy.php:0
2 0.1121 11227224 copyview( ) ../copy.php:32
3 0.1284 11232920 View::create_from_template( ) ../view.php:6518
4 0.1751 11977176 View->copy_contents( ) ../view.php:400
5 0.1820 12520360 BlockInstance->copy( ) ../view.php:5441