This switches the response from a 200, which is not appropriate for invalid requests. Props sheldorofazeroth, johnbillion Fixes #41604 Built from https://develop.svn.wordpress.org/trunk@60301 git-svn-id: http://core.svn.wordpress.org/trunk@59637 1a063a9b-81f0-0310-95a4-ce76da25c4cd