jaredatch/Custom-Metaboxes-and-Fields-for-WordPress — comment on commit c4e86a3a7f5ede72a4cb8126aad7079ebaddbfc6
File: init.php line 433
By GaryJones:

Since you're no longer checking for `$old`, I _think_ this 3rd parameter can be dropped too - each field should already be unique, so checking that it's a certain value before deleting it seems a bit redundant.