===================================================================
RCS file: /cvs/ace/ace/lib/stack.c,v
retrieving revision 1.5
retrieving revision 1.6
diff -p -u -r1.5 -r1.6
--- ace/lib/stack.c	2007/10/22 22:59:41	1.5
+++ /cvs/ace/ace/lib/stack.c	2009/08/23 03:21:17	1.6
@@ -550,6 +550,8 @@ stack_move_cards(Stack *src, int n, Stac
 void
 stack_flip_card(Stack *src, Stack *dest)
 {
+  if (src->num_cards < 1)
+    return;
   stack_note_undo(src, src->num_cards-1, dest);
   doing_undo = 1;
   if (src != dest)
@@ -589,6 +591,8 @@ stack_note_undo(Stack *src, int n, Stack
     else
       undo = (Undo *)malloc(max_undo * sizeof(Undo));
   }
+  if (src->num_cards < 1)
+    return;
   undo[num_undo].src = src;
   undo[num_undo].dest = dest;
   undo[num_undo].count = stack_count_cards(src) - n + 1;