[Delphixml-rpc-public] Workaround for problem with empty strings

[FGM <fg...@os...>]

Apparently, the bug is known and a fix exists in the code. 

When one creates the TRpcCaller, use this:

  var cal    : TRpcCaller ;
      fun    : TRpcFunction ;
      res    : IRpcResult ;
      fields : IRpcArray ;

  begin
  cal := TRpcCaller.Create ;
  cal.HostName := <your host> ;
  cal.EndPoint := <your endpoint> ;
  cal.FixEmptyStrings := True ; // This is the important point

  fun := TRpcFunction.Create ;
  fun.Clear ;
  fun.ObjectMethod := <your method> ;

  fields := TRpcArray.Create ;
  fields.AddItem (<your params>) ;
  <additional params>

  try
    res := cal.Execute (fun) ;