This patch was fed back to the upstream community:

http://code.google.com/p/libarchive/issues/detail?id=287

Given the response "I just committed your patch.", it should

no longer be needed with the next release.

--- libarchive/libarchive/archive_write_set_format_ar.c.orig	Mon Mar 26 19:49:00 2012

+++ libarchive/libarchive/archive_write_set_format_ar.c	Tue Nov 27 17:48:04 2012

@@ -165,7 +165,7 @@

 	 * Reject files with empty name.

 	 */

 	pathname = archive_entry_pathname(entry);

-	if (*pathname == '\0') {

+	if (pathname == NULL || *pathname == '\0') {

 		archive_set_error(&a->archive, EINVAL,

 		    "Invalid filename");

 		return (ARCHIVE_WARN);