segfault fix

ChangeLog

@@ -1,3 +1,7 @@
+2011-03-03 Dietmar Warning
+ * diode & bjt temperature model update tlev, tlevc
+ * cktsgen.c: segfault fix
+
 2011-02-28  Robert Larice
  * src/spicelib/devices/isrc/isrcacct.c ,
  * src/spicelib/devices/isrc/isrcload.c :

src/spicelib/analysis/cktsgen.c

@@ -162,7 +162,7 @@ sgen_next(sgen **xsg)
 
 			if (i >= DEVmaxnum) /* PN: Segafult if not = */
 				done = 1;
-			sg->first_model = sg->next_model = sg->devlist[i];
+			sg->first_model = sg->next_model = (i<DEVmaxnum) ? sg->devlist[i] : NULL;
 
 		} else {
 			done = 1;