new branch ， gitlabBefore=0000000000000000000000000000000000000000

### Jenkins and plugins versions report

Environment

```text
Paste the output here
```

### What Operating System are you using (both controller, and any agents involved in the problem)?

I created the Push hook on GitLab to trigger the Jenkins task. When I create a new branch, modify the file, and submit and putsh it to GitLab. Jenkins gitlabBefore = 0000000000000000000000000000000000000000 in the log, my mission will use gitlabBefore, he seems to be abnormal.
jenkins log as such:
...
gitlabBefore=0000000000000000000000000000000000000000
USER=jenkins
com.apple.java.jvmTask=CommandLine
gitlabTargetBranch=test_jenkins
...

### Reproduction steps

as

### Expected Results

I expect him to return a correct $gitlabBefore

### Actual Results

but it give me gitlabBefore = 0000000000000000000000000000000000000000

### Anything else?

_No response_