Added an additional check for the availability of the STATIC_* settings to...

Added an additional check for the availability of the STATIC_* settings to make sure upgrading a pre-1.3 project doesn't raise a misleading error. Thanks for the report, Florian Apolloner.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14767 bcc190cf-cafb-0310-a4f2-bffc1f526a37