synchronous-process-wait: (copy-output) can be #f

Fix intermittent error: wrong-type-argument #f to integer-zero?.

diff --git a/src/runtime/syncproc.scm b/src/runtime/syncproc.scm
index 16d6b1904a8b0b846a35966934373097d21c5403..d0a7c1093609efa100e6278acd74c8564f5e0d5d 100644 (file)
--- a/src/runtime/syncproc.scm
+++ b/src/runtime/syncproc.scm
@@ -195,7 +195,7 @@ USA.
                    (begin
                      (if redisplay-hook (redisplay-hook))
                      (do ()
-                         ((= (copy-output) 0))
+                         ((= (or (copy-output) 0) 0))
                        (if redisplay-hook (redisplay-hook)))))))))))
   (subprocess-wait* process))
 \f