IDISP001 case we can handle

[JohanLarsson]

            [Test]
            public static void ReturningIfTrueReturnNullReturnItemAfter()
            {
                var code = @"
namespace N
{
    using System;
    using System.IO;

    sealed class C
    {
        MemoryStream M(bool condition)
        {
            ↓var item = new MemoryStream();
            if (condition)
            {
                return null;
            }

            return item;
        }
    }
}";
                RoslynAssert.Diagnostics(Analyzer, ExpectedDiagnostic, code);
            }