Qualtrics Survey Xblock

  Author fields in Studio:
   - Display Name
   - Survey ID
   - Your University
   - Link Text
   - Parameter Name for UserID

  If Parameter Name is left blank, the anonymous student id is
  omitted from the url.

  Links to an already existing Qualtrics survey.
We probably don't want to default this to an invalid ID.

How about 0 or None?