Commerce PDM overwrites existing #after_build in form

The function commerce_pdm_form_commerce_product_ui_product_form_alter overwrites any existing #after_build callbacks when it adds it's own callback. It would be nicer if it would just add to the array of callbacks instead.

The code is:
// Add JavaScript used by form.
$form['#after_build'] = array('_commerce_pdm_product_form_reference_attach');