数据结构调整

@@ -159,8 +159,12 @@ func ToCooperationContractInfo(param *allied_creation_cooperation.CooperationCon
 	}
 
 	for _, v := range param.Undertakers {
+		attachment := v.ContractAttachment
+		if len(attachment) == 0 {
+			attachment = []domain.Attachment{}
+		}
 		u := ContractUndertaker{
-			Attachment: v.ContractAttachment,
+			Attachment: attachment,
 			Department: domain.Department{
 				DepartmentNumber: v.Department.DepartmentNumber,
 				DepartmentId:     int(v.Department.DepartmentId),