How to compare nullable abstracts?

I've came across this while trying to use BigInt library: https://github.com/kevinresol/bigint/issues/3
How is it supposed to support nullability when implementing comparision operators in abstract?
Short example:
```haxe
class Foo {
var i: Int;
public function new(i: Int) this.i = i;
public function eq(f: Foo) return this.i == f.i;
}

abstract AFoo(Foo) from Foo {
@:op(A == B) public inline function eq(o:AFoo):Bool return this.eq(cast o);
}

class Main {
public static function main(): Void {
var i: Null = null;
trace(i == null); // this line works but analogous code here does not: https://github.com/kevinresol/bigint/issues/3
trace(i == new Foo(20)); // exception: Cannot read property 'eq' of null
}
}
```

Start with the linked BigInt issue and reproduce the supplied `Main.main` example involving `Null` and comparison operators. Determine the intended behavior for nullable abstracts and document or validate the resolution against the reported null exception.

Written by the indexing model from the issue text.