GEOAxIS user missing email causes 500 Server Error

[gisjedi]

Description
When a user uses the Login with GEOAxIS functionality and they do not have an email associated with their account, the Scale login flow fails with a 500 Internal Server Error

Reproduction Steps
Steps to reproduce the problem:

1. Go to https://scale.rleu.io/api/login/ as a user that hasn't registered for Disadvantaged User Account.
2. Click on GEOAxIS button under Single sign-on providers
3. Select login with CAC
4. Get redirected to https://scale.rleu.io/api/geoaxis/complete/ with 500 reponse.

Expected behavior
The user is informed of missing email address and directed to register for DUA with GEOAxIS. Alternatively we could just let them through with no email, but that will likely cause things downstream expecting email to break.

Version and Environment Details

• Scale API: v7.0.1-snapshot+25f66235
• Scale UI: v0.16.0