Only populate the spec with truthy values

[horrible-little-slime]

Resolves #79

[Kasekopf]

Is this also a problem for other parts of the spec? Probably familiar, at least

[horrible-little-slime]

Is this also a problem for other parts of the spec? Probably familiar, at least

Looks like familiar is it, based on mousing over some stuff. In particular, everything else is either an object or an array, so it has a default of being empty rather than being nullish

[Kasekopf]

Thanks for the fix!