Fixing problem report 10261 by stopping when ip is closed

svn: r15095

original commit: 10dc76439835021fc5250f38dfa1ecd24355982f

collects/mzlib/port.ss

@@ -1023,6 +1023,8 @@
 (define (regexp-match-evt pattern input-port)
   (define (go nack ch poll?)
     (let try-again ()
+      (if (port-closed? input-port)
+          #f
           (let* ([progress-evt (port-progress-evt input-port)]
                  [m ((if poll?
                          regexp-match-peek-positions-immediate
@@ -1059,7 +1061,7 @@
                      input-port)
                     m2]
                    [poll? #f]
-               [else (try-again)]))]))))
+                   [else (try-again)]))])))))
   (poll-or-spawn go))
 
 (define-syntax (newline-rx stx)