References not disposed when model element is detached.

[mmacfadden]

Versions

• Convergence Version: 1.0.0-rc.5

Describe the Bug
When a model element is deleted, its corresponding references are not disposed.

Step To Reproduce

const realTimeString = model.get("somString");
const ref = realTimeString.indexReference();
realTimeString.removeFromParent();

console.log(ref.isDisposed()) // will return false, should return true.