Index: generic/nsfShadow.c
===================================================================
diff -u -r77b8c1919a102d9309079071f070f2f5b48d50a5 -r719959e71a23301318a68eef99122cd78cf0cc91
--- generic/nsfShadow.c	(.../nsfShadow.c)	(revision 77b8c1919a102d9309079071f070f2f5b48d50a5)
+++ generic/nsfShadow.c	(.../nsfShadow.c)	(revision 719959e71a23301318a68eef99122cd78cf0cc91)
@@ -280,7 +280,7 @@
       level -= topLevel;
     }
 
-    while (++level <= 0 && varFramePtr) {
+    while (++level <= 0 && varFramePtr && framePtr) {
       framePtr = framePtr->nextPtr;
       varFramePtr = varFramePtr->callerPtr;
     }