should eliminate the symptom of pr 7470

svn: r1533
2005-12-05 22:24:00 +00:00 · 2005-12-05 22:24:00 +00:00 · 93a10915fd
commit 93a10915fd
parent de552808de
1 changed files with 1 additions and 0 deletions
--- a/collects/drscheme/private/unit.ss
+++ b/collects/drscheme/private/unit.ss
@ -1304,6 +1304,7 @@ module browser threading seems wrong.
                                 [lst lst])
                        (cond
                          [(zero? n) null]
+                          [(null? lst) null]
                          [else (cons (car lst) (loop (- n 1) (cdr lst)))])))]
                   [find-exp-diff
                    (λ (p1 p2)