bug#57969: 29.0.50; `device-class' errors when NAME is nil

[Lars Ingebrigtsen]

Visuwesh <visuweshm@gmail.com> writes:

> According to the docstring of `device-class', nil is a valid value for
> the NAME argument however it errors out since `x-device-class' uses
> `downcase' without checking if NAME is non-nil.  Backtrace is below,
>
> Debugger entered--Lisp error: (wrong-type-argument char-or-string-p nil)
>   downcase(nil)

Yes --

--
Return the class of the device NAME for an event generated on FRAME.
NAME is a string that can be the value of last-event-device, or
nil.
--

But it's not clear what the meaning of nil should be.  Perhaps Po Lu
knows; added to the CCs.

(And if nil really is a meaningful value for NAME, and not just a
documentation error, then perhaps that argument should be optional?)