Angular fieldmapper editor "new" dialog displays values of recently edited object

In the Angular fieldmapper editor (used on eg2/ admin pages), the "new" dialog should always give you empty fields. But if you edit an object first, then click "New", the dialog acts like the "edit" dialog for the recently edited object, showing those values.

To replicate:

- Go to /eg2/en-US/staff/admin/acq/cancel_reason
- Click "New Cancel Reason"
- Confirm that dialog fields are empty
- Click "Cancel"
- Edit a row (by double clicking, or selecting and clicking "Edit Selected" in actions menu)
- Notice the populated values, such as the ID
- Click "Cancel"
- Click "New Cancel Reason" again
- Confirm that dialog fields are not empty, but contain values from previously edited object