bug#3998: 23.1; process status

[Stefan Monnier]

> (process-status nil) returns an error (please see below) in spite of
> it's documentation claiming that it's argument can indeed be nil.

It says that if the argument is nil, process-status will use the current
buffer's process.  But if the current buffer doesn't have any process,
then of course it'll signal an error.  That's why the error is:

                 Buffer gasket_tilting.mac has no process
rather than
                 nil is not a valid process


-- Stefan