Fix migration panic due to an empty review comment diff (#28334)

Fix #28328 
```
func (p *PullRequestComment) GetDiffHunk() string {
	if p == nil || p.DiffHunk == nil {
		return ""
	}
	return *p.DiffHunk
}
```
This function in the package `go-github` may return an empty diff. When
it's empty, the following code will panic because it access `ss[1]`

ec1feedbf5/services/migrations/gitea_uploader.go (L861-L867)

ec1feedbf5/modules/git/diff.go (L97-L101)
This commit is contained in:
Nanguan Lin 2023-12-05 16:29:43 +08:00 committed by GitHub
parent a95d5b7702
commit 49b98e45bc
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@ -862,7 +862,7 @@ func (g *GiteaLocalUploader) CreateReviews(reviews ...*base.Review) error {
line := comment.Line
if line != 0 {
comment.Position = 1
} else {
} else if comment.DiffHunk != "" {
_, _, line, _ = git.ParseDiffHunkString(comment.DiffHunk)
}