FilterTypes produce schema errors when filters properties are nullable.

[michaelstaib]

Describe the bug
FilterTypes produce schema errors when filters properties are nullable.

To Reproduce

public class FooNullable
{
    public short? BarShort { get; set; }
}

[Fact]
public void Model_With_Nullable_Properties()
{
    // arrange
    // act
    var schema = CreateSchema(
        new FilterInputType<FooNullable>(
            d => d.Filter(f => f.BarShort)));

    // assert
    schema.ToString().MatchSnapshot();
}

Expected behavior
The schema correctly is created without any schema error.

Desktop (please complete the following information):

• OS: macOS
• Version: HotChocolate Version 10.0.0

[michaelstaib]

This one is now fixed with #1170