null argument despite "non-null" name.

[progfolio]

Managing State > "sb" a bunch of infixes

For the --non-null option, if the user accepts an empty prompt the option is null.

To reproduce:

1. M-x ts-show case
2. s b
3. - n RET
4. s to show arguments

The output is:

prefix-arg: nil
prefix's scope value: nil
transient-args: nil

[psionic-k]

magit/transient#228 Upstream change is necessary to fully resolve