NRE when constant field has null value

[batkaevruslan]

FindTypesThatHaveDependencyOnAny fails with NRE when examined type has constant field with null value

public class Class_C
{
    private const string NullConstant = null;
    Dependency_2 dp2;      
}

Repro master...batkaevruslan:NetArchTest:const-field-dependency-issue fails test