Tries to set value on undefined object

[jsumners]

At https://github.com/jleibund/exprjs/blob/master/lib/expr.js#L1474 it can happen that obj = undefined, thus node.object was never created and setting node.object.value = obj will throw a reference error.

[jsumners]

The issue crops up due to type coercion at https://github.com/jleibund/exprjs/blob/master/lib/expr.js#L1304 . Given the following context:

{
  foo: null
}

If we evaluate the expression foo !== null then the check ref && ref != undefined will result in false when it should really be true. Thus, the check should be ref !== undefined.

[jleibund]

I apologize for not actively maintaining this. If you have time to submit a PR for this I will gladly merge it in.

[jsumners]

I'll try to find some time to submit a PR. I don't actually use the module right now (I abandoned the project I needed it for), but I may discover a use for it again. It's a nice tool to have.