Event registration API call returns DB error

When using the cid=0 version of event registration pages (4.4.x+), the user (with the right permissions) can select a contact through an autocomplete API call to register.

If the event has a bottom profile selected for the online registration, the AJAX call returns a DB Error due to a syntax error. It appears the API expects a single profile ID to be passed through, but with the bottom profile, it can be multiple profiles, so the data structure passed is an array of IDs. This is causing the query to fail. This is the response from the AJAX call (from browser console):

{"is_error":1,"error_message":"DB Error: syntax error"}

I have recreated this error on both our 4.4.8 installation and the demo site. The instructions to do so are as follows:

1. Create a new event with online registration enabled.
2. On the Online Registration tab of the event configuration screen, select any profile in the Include Profile (bottom of the page) field.
3. After saving, click the Online Registration (live) link, then click the link to register a different person.
4. Select any contact from the Select another person autocomplete box.

At that point, the contact's information should fill into the registration form, but this error is preventing that from happening.