Templating: Json interpolation of single-value default selection does not create valid json

[kaydelaney]

Fixes an issue where, if a template variable with options doesn't have a value selected, the default value picked wasn't wrapped in an array as it would be if a user were to select it themselves.

Effectively the old value was

{
    value: option.value,
    text: option.text,
    selected: true,
}

where the new value is

{
    value: typeof option.value === 'string' ? [option.value] : option.value,
    text: typeof option.text === 'string' ? [option.text] : option.text,
    selected: true,
}

So value and text are wrapped in an array if they are plain strings.

[axelavargas]

🏅 Nice, this one was a bit tricky to reproduce, I also noticed the problem when the default variable is not in the options (maybe an old option configured).

Great job figuring this one, @kaydelaney 🙌🏾