search for duplicates fails on new record creation when civicrm_engage is installed

If you have civicrm_engage installed, you have the add new contact form open, and you click on the "Check for Matching Contacts" button, you get the following error:

Sorry. A non-recoverable error has occurred.
One of parameters (value: ) is not of the type Integer

It seems to be caused by the postProcess hook in the civicrm_engage module, which should not execute when de-duping, only when a contact is actually being added.