Ticket #56485: 56485.patch

src/wp-includes/formatting.php

@@ -2779 +2779 @@
  * @return string String without the trailing slashes.
  */
 function untrailingslashit( $string ) {
-        return rtrim( $string, '/\\' );
+        if ( ! empty( $string ) ) {
+                $string = rtrim( $string, '/\\' );
+        }
+        return $string;
 }
 
 /**