inpgmod.c, plug a memory hole

Reported and fixed by Marek Bielik in message:
  Subject: [Ngspice-devel] Memory leaks fix
  Date: Tue, 18 Apr 2017 16:16:21 +0000

src/spicelib/parser/inpgmod.c

@@ -81,8 +81,10 @@ create_model(CKTcircuit *ckt, INPmodel *modtmp, INPtables *tab)
 
     while (*line) {
         INPgetTok(&line, &parm, 1);
-        if (!*parm)
+        if (!*parm) {
+            FREE(parm);
             continue;
+        }
 
         for (j = 0; j < *(ft_sim->devices[modtmp->INPmodType]->numModelParms); j++) {