Allow 0 as value in multi-context settings

[hugopeek]

What does it do?

This accepts 0 values as non-empty for multi-context settings.

Why is it needed?

When using ClientConfig in multi-context mode, you can't set an actual value of 0 (tested with numberfield and selectbox). This causes the setting to fall back on the global value.

I don't know if this is a bug or a design choice, but in my opinion 0 does not always equate to empty here. So I propose to return 0 as context-specific value, instead of the global fallback.

Remarks

I hope this won't break anyone's existing setup. It's also a little tricky to select a truly empty option in a selectbox, because the following doesn't work:

Global==||Low==0||Medium==1||High==2

In this case, Global is returned if you select the first option. Also a little bug maybe? Because this would work with TVs.. In any case, this does work:

||Low==0||Medium==1||High==2

This renders and empty first option and when selected, the global value is returned. Not the prettiest solution, but at least it allows you to replicate the old behaviour. A reset option similar to the one for TVs would be nice here of course, but that's probably a little too much to ask for ;)

[sebastian-marinescu]

Hi Hugo, nice PR 👍

Just noticed this behavior, in a theme-case:

Knowing the behavior after your PR would allow me to "fix" it, and add a description telling the editor that the first blank option is actually the global option (which I'm thinking of introducing there ^).

But certainly this

Global==||Disabled==0||Enabled==1

would be much nicer.

Don't you think we could make Global== possible, by fixing the code that splits this into key/value?
( I think this is the culprit: https://github.com/modmore/ClientConfig/blob/master/assets/components/clientconfig/js/mgr/sections/home.js#L186 )