(Bug 5221) Fix uninitialized value warning in DW::SiteScheme

Use of uninitialized value $rv in hash element
 at /dreamhack/home/8398-kareila/dw/cgi-bin/DW/SiteScheme.pm line 199.
Merge pull request #528 from kareila/5221-warnings

(Bug 5221) Fix uninitialized value warning in DW::SiteScheme