@@ -27,10 +27,18 @@
      (define-syntax name (syntax-rules () ((name arg ...) (begin body ...)))))))
 
 (define-syntax common:handle-exceptions
   (syntax-rules ()
     ((_ exn-in errstmt ...)(handle-exceptions exn-in errstmt ...))))
+
+(define (safe-vector-ref vec indx)
+  (if vec
+      (vector-ref vec indx)
+      (begin
+	(debug:print 0 "vector-ref called with #f")
+	(print-call-chain (current-error-port))
+	(exit))))
 
 (define (debug:calc-verbosity vstr)
   (cond
    ((number? vstr) vstr)
    ((not (string?  vstr))   1)