The real solution. If the sendreq->req_send.req_bytes_packed is zero then there

is no data to be trasfered. And this is the condition which lead to a non
initialized convertor.

This commit was SVN r10299.

ompi/mca/pml/ob1/pml_ob1_sendreq.h

@@ -298,7 +298,7 @@ do {
             MCA_PML_OB1_SEND_REQUEST_RETURN( sendreq );                                 \
         } else {                                                                        \
             if(sendreq->req_send.req_base.req_ompi.req_persistent &&                    \
-               (0 != sendreq->req_send.req_base.req_count) ) {                          \
+               (0 != sendreq->req_send.req_bytes_packed) ) {                            \
                 /* rewind convertor */                                                  \
                 size_t offset = 0;                                                      \
                 ompi_convertor_set_position(&sendreq->req_send.req_convertor, &offset); \