1 files changed, 9 insertions, 8 deletions
diff --git a/variable.c b/variable.c
index 39f0ada..54bbc02 100644
--- a/variable.c
+++ b/variable.c
@@ -674,16 +674,17 @@ merge_variable_set_lists (struct variable_set_list **setlist0,
 
   /* This loop relies on the fact that all setlists terminate with the global
      setlist (before NULL).  If that's not true, arguably we SHOULD die.  */
-  while (setlist1 != &global_setlist && to != &global_setlist)
-    {
-      struct variable_set_list *from = setlist1;
-      setlist1 = setlist1->next;
+  if (to)
+    while (setlist1 != &global_setlist && to != &global_setlist)
+      {
+        struct variable_set_list *from = setlist1;
+        setlist1 = setlist1->next;
 
-      merge_variable_sets (to->set, from->set);
+        merge_variable_sets (to->set, from->set);
 
-      last0 = to;
-      to = to->next;
-    }
+        last0 = to;
+        to = to->next;
+      }
 
   if (setlist1 != &global_setlist)
     {