Use correct variable. We preg_match() against $request_match, so that's what...

Use correct variable. We preg_match() against $request_match, so that's what should be checked with empty() too. Fixes #17177.


git-svn-id: https://core.svn.wordpress.org/trunk@19280 1a063a9b-81f0-0310-95a4-ce76da25c4cd