When using the Build User Vars Plugin in Jenkins, the BUILD_USER_ID parameter is not set in a downstream job if the upstream job was triggered using Generic Cause(gitlab webhook). The downstream job, triggered by the upstream job, does not receive information about the user who initiated the process, causing issues with tracking user actions. Additionally, the logs show Unsupported cause type(s):...

Steps to Reproduce:

1. An upstream job (Job A) is triggered via Generic Cause.
2. Job A triggers a downstream job (Job B).
3. Job B has the Build User Vars Plugin enabled to capture the BUILD_USER_ID parameter.
4. Trigger Job A through Generic Cause.
5. In Job B, the BUILD_USER_ID variable is missing.

Expected Behavior:
The BUILD_USER_ID variable should be available in Job B and should contain the ID of the user who initiated Job A, even when triggered through Generic Cause.

Actual Behavior:
In Job B, the BUILD_USER_ID variable is missing, despite the Build User Vars Plugin being enabled.

This issue occurs only in job chains where the upstream job is triggered via Generic Cause.
If Job A is triggered manually, the BUILD_USER_ID variable is correctly set and available in Job B.