Try to figure out attribute checker problem (#33901) (#33902)

Backport #33901

services/gitdiff/gitdiff.go

@@ -1193,6 +1193,8 @@ func GetDiff(ctx context.Context, gitRepo *git.Repository, opts *DiffOptions, fi
 				if language.Has() {
 					diffFile.Language = language.Value()
 				}
+			} else {
+				checker = nil // CheckPath fails, it's not impossible to "check" anymore
 			}
 		}