Content type attributes with falsey values lead to a value of undefined in event payload

[ibarreto]

Describe the bug
There's a bug here where if the value of a property is falsey (false, '', etc.) then separatorExtraction(prop) evaluates to falsey, which would be the case for when we have something like "property$en": false, then the code will evaluate nestedDictExtraction(prop), and that nested dictionary might not be defined in the content type and thus return undefined, so we end up with a property: undefined in the payload.

To Reproduce
Have a content element where the type is boolean and is set to false, where it uses the property$language separator.

Expected behavior
Instead of getting undefined in the payload, we should have false (or the relevant falsey value)

Environment (please complete the following information):

• Botpress Version: 12.31.8 (but bug has been around for longer)

Additional context
Add any other context about the problem here.