Gitlab test webhooks got 500 page

Summary

Click test webhooks always got 500 page

Steps to reproduce

I have a self-host gitlab by docker image, and hosted jenkins at another server. I use gitalb-plugin to generate a build trigger webhooks which added at gitlab. But when I click test webhooks button. I always got a 500 page. I have add slack webhooks and it works fine. I am not sure which step is wrong.

Results of GitLab environment info

gitlab: latest docker image jenkins: latest jenkins image