Expression and not

[FAMILIAR-project]

There is an assert in Expression class...
The "not" expression seems impossible to create without a third null parameter, but it violates the assertion.

Maybe a solution is to cast the null with Expression

It is a FAMILIAR bug

public Expression(T feature) {
        assert feature != null;

        this._type = ExpressionType.FEATURE;
        this._feature = feature;
    }

private Expression<String> mkFeatureNodeNot(FeatureNode<String> v) {
        return new Expression(ExpressionType.NOT, (String)v.getFeature(), (Object)null);
    }