[GITEA] Skip unsupported code comment

- If there's a code comment that's received during the migration that
contains no diffhunk, skip it. This either means it was commenting on
old diffhunk or it's just a general codecomment. Forgejo supports
neither of such type of code comment.
- Resolves https://codeberg.org/forgejo/forgejo/issues/1407

(cherry picked from commit ae463c7c55)
(cherry picked from commit bf48f02a86)
(cherry picked from commit 10c3f102fa)
(cherry picked from commit 828b4cc10c)
(cherry picked from commit 6427fa65b6)

services/migrations/gitea_uploader.go

@@ -859,6 +859,11 @@ func (g *GiteaLocalUploader) CreateReviews(reviews ...*base.Review) error {
 		}
 
 		for _, comment := range review.Comments {
+			// Skip code comment if it doesn't have a diff it is commeting on.
+			if comment.DiffHunk == "" {
+				continue
+			}
+
 			line := comment.Line
 			if line != 0 {
 				comment.Position = 1