bug#56038: Unable to edit booleans with 'help-fns-edit-variable'

[Stefan Kangas]

I'm unable to edit booleans with `help-fns-edit-variable'.

For example, if I have this "*Help*" buffer

    help-enable-variable-value-editing is a variable defined in ‘help-fns.el’.

    Its value is t
    Original value was nil

and put point on `t' on the second to last row, and then type `e', I get
the error "e is undefined".  My expectation is that I should be able to
edit this value.

I see the same with e.g. `project-ignore-buffer-conditions' (whose value
isnil), but not with some other random variable e.g. `comp-num-cpus'.

In GNU Emacs 29.0.50 (build 3, x86_64-pc-linux-gnu, GTK+ Version
3.24.24, cairo version 1.16.0)
 of 2022-06-17 built on joffe
Repository revision: dc6157bef758cf5ba490219eebccaf33e14430d3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)