ComponentDesigner.PostFilterAttributes(null) throws NRE

[hughbe]

public static IEnumerable<object[]> PostFilterAttributes_TestData()
{
    yield return new object[] { null, InheritanceAttribute.Default };
    yield return new object[] { new Dictionary<Type, object>(), InheritanceAttribute.Default };
    yield return new object[] { new Dictionary<Type, object> { { typeof(InheritanceAttribute), null } }, InheritanceAttribute.Default };
    yield return new object[] { new Dictionary<Type, object> { { typeof(InheritanceAttribute), new object() } }, InheritanceAttribute.Default };
    var attribute = new InheritanceAttribute();
    yield return new object[] { new Dictionary<Type, object> { { typeof(InheritanceAttribute), attribute } }, attribute };
}

[Theory]
[MemberData(nameof(PostFilterAttributes_TestData))]
public void PostFilterAttributes_HasInheritanceAttributeKey_Sets(IDictionary attributes, object expected)
{
    var designer = new SubComponentDesigner();
    designer.PostFilterAttributes(attributes);
    Assert.Same(expected, designer.InheritanceAttribute);
}