bug in examples:compare.lisp

[Michael Travers <mt@media.mit.edu>]

The C-x d command (buffer-to-buffer compare) doesn't work if the
buffer selected from the dialog doesn't have a pathname (ie, if it's a
new buffer).  Here's a patch:

(defun select-diff-buffer (current)
  (car (select-item-from-list
        (delete-if #'(lambda (w) (typep w 'listener))
                   (remove current (windows :class 'fred-window :include-invisibles t)))
        :table-print-function #'(lambda (w stream) (princ (or (window-filename w) (window-title w)) stream))
        :window-title (format  nil "Compare \"~A\" to:" (window-filename current)))))