Return false from wp_get_referer() if it is called before wp_validate_redirect() is defined.

see #25294.


git-svn-id: https://develop.svn.wordpress.org/trunk@25399 602fd350-edb4-49c9-b593-d223f7449a82
Return false from wp_get_original_referer() if it is called before wp_validate_redirect() is defined.

see #25294.


git-svn-id: https://develop.svn.wordpress.org/trunk@25400 602fd350-edb4-49c9-b593-d223f7449a82