Default empty merger list to those with write permissions (#12535) (#12560)

Backport #12535

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

services/pull/merge.go

@@ -544,7 +544,7 @@ func IsUserAllowedToMerge(pr *models.PullRequest, p models.Permission, user *mod
 		return false, err
 	}
 
-	if (p.CanWrite(models.UnitTypeCode) && pr.ProtectedBranch == nil) || (pr.ProtectedBranch != nil && pr.ProtectedBranch.IsUserMergeWhitelisted(user.ID)) {
+	if (p.CanWrite(models.UnitTypeCode) && pr.ProtectedBranch == nil) || (pr.ProtectedBranch != nil && pr.ProtectedBranch.IsUserMergeWhitelisted(user.ID, p)) {
 		return true, nil
 	}