Issue:Articlecategory doesn't work in 1.6.8

Description:	articlecategory produces no output
Extension / Version:	DPL   /   1.6.8
Type / Status:	Bug   /   open

Problem

This example produces no output on MediaWiki 1.11.x and 1.12.0 on Windows 2003 Server.

<dpl>
namespace = Talk
articlecategory = My category
</dpl>

even if there are articles in "My category" that have talk pages. I would expect to see a bulleted list of all Talk pages whose main article is in "My category".

This problem exists in DPL 1.6.5 as well.