下面的代码抛出一个错误
可能为空引用的解引用
在带有注解的行：

using System.Security.Cryptography.X509Certificates;

public class LowLevelClass
{ 
    public async Task? SomeMethod()
    {
        await Task.Run(() => Console.WriteLine("Hello"));
    }
}

public class TopLevelClass
{
    private LowLevelClass? lowLevelClass = null;

    public TopLevelClass()
    { 
        lowLevelClass = new LowLevelClass();
    }

    public async Task? SomeOtherMethod()
    {
        if(lowLevelClass != null)
            await lowLevelClass.SomeMethod(); // Dereference of possibly null reference
    }
}

public static class Program
{
    public static void Main()
    {
        TopLevelClass topLevelClass = new TopLevelClass();
        Task t = Task.Run(async () => await topLevelClass.SomeOtherMethod());
        t.Wait();
    }
}

我认为这是由于LowLevelClass.SomeMethod可能返回null Task。
如何避免警告？
我尝试为lowLevelClass对象插入非空条件或将代码修改为

await lowLevelClass?.SomeMethod();

但没有成功