'cd' built-in crashed zsh on a broken file system

[Kamil Dudka <kdudka@xxxxxxxxxx>]

The following bug report describes a crash of the 'cd' built-in of zsh:

https://bugzilla.redhat.com/1183238

The root cause was probably an inconsistent state of the sshfs file system 
after resume from suspend-to-ram.  However, the segmentation fault suggests 
there might be some insufficient error handling in zsh code.

unmeta() was called with NULL as pwd at the following line:

http://sourceforge.net/p/zsh/code/ci/638bfa93/tree/Src/builtin.c#l807

It is not clear to me why pwd was NULL after the return from cd_new_pwd()
and I was not able to trigger the bug myself to debug it further.  The full 
backtrace is available here:

https://bugzilla.redhat.com/attachment.cgi?id=981010

Kamil