Descripción: Users receive a "User is Null" error while trying to launch an LTI link from an email notification sent from the Partner/Third party's system.

Pasos para repetir:

1. Log into Blackboard Learn Ultra Experience as an administrator 
2. Install an LTI 1.3 tool
3. Create an LTI item (either an LTI 1.3 or a deep link item)
4. Query through the Assignments and Grade Service or REST API the content ID and Course ID of the LTI item and course
5. Build a URL with the following format:

https://<BB_INSTANCE_URL>/webapps/blackboard/execute/blti/launchLink?course_id=<BB_CONTEXT_ID>&from_ultra=true&content_id=<BB_RESOURCE_ID>

E.g: https://bbultra.ddns.net/webapps/blackboard/execute/blti/launchLink?course_id=_4_1&from_ultra=true&content_id=_23_1

Observed Behavior:
 Link launches if the user already has the session but it shows the error "User is null" if the session has expired or there's no session in cache

Expected Behavior:
 Link launches if the user already has a session or is redirected to the login page if the session has expired.