title: MembershipUser constructor expects dateTime fields that might be null
body: <p>The MemberShipUser constructor expects dateTime fields like lastLoginDate, which may be null in the data store. </p>
  
  <p>However, when I retrieve data from the store and pass null in for the parameter, I get an error that it cannot be null.</p>
  
  <p>How can I work around this?</p>