Ticket #24618: enhance.vun.diff

wp-includes/user.php

@@ -1226 +1226 @@
  */
 function validate_username( $username ) {
         $sanitized = sanitize_user( $username, true );
-        $valid = ( $sanitized == $username );
+        $valid = !empty($sanitized) ? ( $sanitized == $username ) : false;
         return apply_filters( 'validate_username', $valid, $username );
 }