FileTransferNegotiatot null pointer exception processing the stream initiation response

When the server returns a data form with one of field without a the var attribute, as a response of a stream initiation stanza, the FileTransferNegotiator throws a null pointer exception when it inspects that field looking for the stream-method. Returning this kind of data form might be an error from the server side but the FileTransferNegotiator could avoid this with a simple change.