On the final segment the SDO shoud be written using the
pre-allocated buffer used to store segments during transfer.
Whecn completed the pre-allocated buffer is written to the SDO.
This fix change to correct complete_access_subindex_loop
buffer, ESCvar.mbxdata
to use the lookup indexes for ESCVar.index -> nidx and
ESCvar.subindex -> nsub.
On the final segment the SDO shoud be written using the pre-allocated buffer used to store segments during transfer. Whecn completed the pre-allocated buffer is written to the SDO. This fix change to correct complete_access_subindex_loop