ZD#846948 APPS-1917 Fetch tickets even if email and phone are missing

:koala:

This PR changes the guard of tickets fetching to check the presence of user object and id attribute.
It no longer aborts ticket fetching when the user is missing email address and phone number.

/cc @zendesk/quokka 

### REFERENCE
- [JIRA APPS-1917](https://zendesk.atlassian.net/browse/APPS-1917)

### RISKS
- N/A