GraphQL layer treats `0` as `null`

[m-mitchell]

If you pass an explicitly-set 0 value through the graphQL layer, it gets silently dropped because 0 is falsy in JS and the checks in the graphQL layer aren't very specific. I have a nullable integer field where 0 and null mean two different things, but when I send a 0, it gets converted to null.

You can see the issue in this method: https://github.com/jagql/framework/blob/master/lib/graphQl/resolvers.js#L66