Add _baseUri to _queryBuilder when url is null or empty in MailSendController

[Break-1T]

pepipost-sdk-csharp/Pepipost/Controllers/MailSendController.cs

Line 79 in 19425ab

_queryBuilder.Append("/mail/send");

           if (string.IsNullOrWhiteSpace(url))
           {
               _queryBuilder.Append(_baseUri +"/mail/send");