fix(session): Ensure token and UID are valid

[solracsf]

Summary

Fix for:

"File": "/var/www/nextcloud/lib/private/User/Session.php",
    "Line": 415,
    "message": "Call to a member function getEMailAddress() on null",
    "exception": [],
    "CustomMessage": "Call to a member function getEMailAddress() on null"

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)