slab dipole correction in one-electrode TranSIESTA calculation

I have a question regarding slab dipole correction: should it also be true for a one-electrode calculation using TranSiesta? However, I found in dhscf.F, line 466-469 (version 4.1-b1):

              if ( ts_tidx < 1 ) then
                 call die('Error, electric field and undetermined &
     &transport direction does not make sense!')
              end if

These lines prevent setting a slab dipole correction for one-electrode transport calculation in my case. My system and coordinates are the following: start with a standard two-electrode molecular junction setup, delete one electrode (those atoms with the larger z-coordinates), but keeps the box unchanged so that there is vacuum on the molecule side. My coordinates starts with z=a/2 where a is the spacing between atomic layers in the electrode along z and the transport direction (assuming the original two-electrode setup) is along z. I actually don't know why I have ts_tidx < 1 in my case.

From my experience, I need the slab dipole correction set true in a one-electrode TranSiesta calculation in order to match the physically correct results (electrostatic potential and PDOS) from a standard Siesta calculation of the slab with dipole correction.

I know there is a post in the "bugs" session regarding slab dipole correction, but it does not discuss the transport case. In order not to confuse discussion there, I decide to ask this question here.

Thanks!