scsh 0.5.2 typo in procobj.scm

[Gary Houston <ghouston@arglist.com>]

The last line of procobj.scm/filter-weak-ptr-list seems incorrect.
It was OK in 0.5.1:

(define (filter-weak-ptr-list pred lis)
  (fold-right (lambda (wptr result) (let ((val (weak-pointer-ref wptr)))
                                      (if (and val (pred val))
                                          (cons wptr result)
                                          result)))
              '()
              list))