io.c: fix fptr_copy_finalizer

* io.c (fptr_copy_finalizer): fix inverted condition.  if
  finalizer does not change, pipe_list should not change too.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62145 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

io.c

@@ -6201,12 +6201,14 @@ fptr_copy_finalizer(rb_io_t *fptr, const rb_io_t *orig)
 {
 #if defined(__CYGWIN__) || !defined(HAVE_WORKING_FORK)
     void (*const old_finalize)(struct rb_io_t*,int) = fptr->finalize;
+
+    if (old_finalize == fptr->finalize) return;
 #endif
 
     fptr->finalize = orig->finalize;
 
 #if defined(__CYGWIN__) || !defined(HAVE_WORKING_FORK)
-    if (old_finalize == pipe_finalize) {
+    if (old_finalize != pipe_finalize) {
 	struct pipe_list *list;
 	for (list = pipe_list; list; list = list->next) {
 	    if (list->fptr == fptr) break;