#29 Allow "write" to save emtpy vectors (array with 0 elements) when ".option savecurrents" is active.

[astx]

ngspice 30+ pre-master: allow "write" to save emtpy vectors (array with 0 elements) when ".option savecurrents" is active.
Necessary for a bigger ngspice script which does tran, ac, linearize and other simulations in one step.
Status: works for me

[Holger Vogt]

There is now a function 'remzerovec' on master branch (and upcoming ngspice-32) which removes all zero length vectors. This is a better solution to the aboive mentioned problem than some very special exception handling in a general parser.