Fix S1168: Rule should not report when returning null within a lambda

[Evangelink]

Description

Currently the rule raises an issue when returning null from within a lambda declared inside of a method returning a collection.

Repro steps

public List<int> Method()
{
    Func<int?> aFunc = () => {
        return null;
    };
    return new List<int>();
}

Related information

• SonarLint for VS 3.5.0.1803