[REPOST PATCH xauth] Don't crash when running past the end of the chain

[Egbert Eich]

Hi!

On August 14 I've reposted three patches for xauth to this mailing list.
I did so, because I had discovered that a 'Dr. Tilmann Bubeck' has added
himself as maintainer of the xauth package to the xorg/doc/xorg-docs/MAINTAINERS
file on Jan. 22 2013 - considering the change frequency of this file this 
is not that long ago.
The only reply I ever got on any of the 3 posts was by Walter Harms.

So I did a quick check in the xauth package which did not turn up any
contribution by this individual.

After doing further investigations I concluded that this commit apparently 
was the only thing that he has ever contributed to any X.Org related package.

Research on Google did not turn up any relevant affiliation to any X.Org 
related software.

For this change his name and email address is listed not only for the author
but also for the committer.

This begs the question how did this commit ever get into the xorg-docs
package?
Did he commit this change himself - and if so, how did he get commit 
access to the X.Org repos?
Or if he didn't do it himself (and he may not even be aware of this commit), 
who else did - using his name and email?

Cheers,
	Egbert.