Prevent crash if EXTERNAL voltage source is used

Fixes
98763c0ad ("Note: ix: dc value used for op instead of transient time=0 value Former warning message or note only issued when dc value and value at transient time=0 differ.", 2022-09-20)

src/spicelib/devices/vsrc/vsrctemp.c

@@ -48,7 +48,9 @@ VSRCtemp(GENmodel *inModel, CKTcircuit *ckt)
                     here->VSRCname);
             }
             else if (here->VSRCdcGiven && here->VSRCfuncTGiven
-                     && here->VSRCfunctionType != TRNOISE && here->VSRCfunctionType != TRRANDOM) {
+                     && here->VSRCfunctionType != TRNOISE
+                     && here->VSRCfunctionType != TRRANDOM
+                     && here->VSRCfunctionType != EXTERNAL) {
                 /* DC value and transient time 0 values given */
                 double time0value;
                 /* determine transient time 0 value */