check that we can survive emptiness

* (exec-spice "ngspice -b %s")

* Nothingness, No circuit elements at all.
*   We have only the implicit node "0"
* Checks whether we can live with a
*   zero times zero circuit matrix

.control
op
tran 0.1m 1m
ac lin 3 1kHz 2kHz
echo "TEST: done"
quit 0
.endc

.end