Cannot turn off or edit confirmation emails when registering participants via Manage Events

The email_receipt fieldset is not "shown" in the Participant form if the form is loaded in standalone mode with a specific event (eid=N) AND the specified event is FREE (no fees). In this condition, even if I then change the selected event - the email_receipt fieldset does not load. This problem does NOT occur if the eid is a paid event.

To replicate:

• create a free event
• click "Register Participant" from the Event Links sub-menu or button (top of Configure tabs)
• select a contact who has a valid email address
  Registration Confirmation fieldset is not loaded.

If I load the form in standalone w/o selecting an event (from Create button or Events menu > Register Participant) - when I select the free event things work fine.

In the error flow, I'm seeing a jScript error which MAY be the cause:
—
Error: syntax error
Source File: http://civicrm42/sites/civicrm42/modules/civicrm/packages/jquery/jquery.min.js?m0j5iw
Line: 10, Column: 40
Source Code:
var eventFeeBlockValues = ;

—

— Original Post —
In a certain participant registration workflow from Manage Events, the option to turn off email confirmations, select a 'from' email, or enter a confirmation message doesn't appear. The buildFeeBlock function is not working in some cases.

Reproduced on demo site. Screenshots attached.