error getting working directory

[ParityError]

If you're in a directory that no longer exists and attempt to run any commands relating to MacPorts you'll get an error:

$ cd ~/desktop
$ mkdir test
$ cd $_
$ rm -rf ../test
$ port search xorg-server
error getting working directory name: no such file or directory
    while executing
"pwd"
    invoked from within
"set current_portdir [pwd]"
    (file "/opt/local/bin/port" line 5725)

Yes, it's a strange to remove a directory that you are pwd, but maybe MacPorts should have some type of check in that circumstance?