[1.1.X] Fixed #11764 -- Added a missing set of parentheses in a call...

[1.1.X] Fixed #11764 -- Added a missing set of parentheses in a call calculating the select_related tables. Thanks to aurelio for the report and original patch, and wogan for the updated patch.

Backport of r13019 from trunk.

git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.1.X@13020 bcc190cf-cafb-0310-a4f2-bffc1f526a37