Allow optional parameter to be nil

* lisp/ibuf-ext.el (ibuffer-copy-filename-as-kill): Allow the
optional parameter to be nil (bug#21576).

1 files changed, 1 insertions, 1 deletions

diff --git a/lisp/ibuf-ext.el b/lisp/ibuf-ext.el
index aa3ccbd40f7..6052bf32ce3 100644
--- a/lisp/ibuf-ext.el
+++ b/lisp/ibuf-ext.el
@@ -1403,7 +1403,7 @@ You can then feed the file name(s) to other commands with \\[yank]."
   (if (zerop (ibuffer-count-marked-lines))
       (message "No buffers marked; use 'm' to mark a buffer")
     (let ((ibuffer-copy-filename-as-kill-result "")
-          (type (cond ((zerop arg)
+          (type (cond ((or (null arg) (zerop arg))
                        'full)
                       ((= arg 4)
                        'relative)