Fix from Holger Vogt for two cinditions that caused segfault.

ChangeLog

@@ -1,3 +1,9 @@
+2007-12-31 Holger Vogt
+ * src/frontend/com_chdir.c: fix for the crashing of ngspice under Windows when
+   started from windows explorer.
+ * src/frontend/inp.c: ngspice crashed when executing a file consisting of a simple
+   control section. Fixed.
+
 2007-12-29 Dietmar Warning
  * src/frontend/inpcom.c: 3/4 terminal recognition for bjt's
  * src/misc/string.c, stringutil.h: token function for bjt instance

src/frontend/com_chdir.c

@@ -49,9 +49,9 @@ com_chdir(wordlist *wl)
     }
 
 
-
-    if (*s && chdir(s) == -1)
-        perror(s);
+    if (s != NULL)
+       if (chdir(s) == -1)
+           perror(s);
 
     if (copied)
 	tfree(s);

src/frontend/inp.c

@@ -534,8 +534,10 @@ inp_spsource(FILE *fp, bool comfile, char *filename)
       }     /*  if (deck->li_next) */
 
       /* look for and set temperature; also store param and .meas statements in circuit struct */
-      ft_curckt->ci_param = NULL;
-      ft_curckt->ci_meas  = NULL;
+      if (ft_curckt) {
+          ft_curckt->ci_param = NULL;
+          ft_curckt->ci_meas  = NULL;
+      }
 
       for (dd = deck; dd; dd = dd->li_next) {
 	/* get temp after numparam run on deck */