Invalid verbs do not cause errors if a default verb is set

Issue に示されている Parser.ParseArguments 呼び出しから始め、デフォルト動詞を有効にした状態で DefaultVerb.exe foo を使用して動作を再現します。デフォルト動詞が存在する場合に認識されない動詞がどのように処理されるかを追跡し、その後、無効な入力が DoSomething やデフォルト動詞ではなくエラーパスに到達することを確認します。

Below is a very simplified C# console application I called DefaultVerb. Running the application with start or finish works as expected, outputting Start or Finish correctly, but if I run the application with DefaultVerb.exe foo, it outputs Start. If I set isDefault to false, and run DefaultVerb.exe foo I receive the following expected error:
ERROR(S): Verb 'foo' is not recognized. --help Display this help screen. --version Display version information.
When I have isDefault: true on my verb, what should be the behavior if I pass in an invalid verb? I'm not expecting a bad verb to run my default verb.

`
using CommandLine;
using System;

internal class Program
{
[Verb("start", isDefault: true, HelpText = "start help")]
class StartOptions
{
}

[Verb("finish", HelpText = "finish help")]
class FinishOptions
{
}

static void Main(string[] args)
{
    var parser = new Parser(settings =>
    {
        settings.AutoVersion = false;
        settings.CaseSensitive = false;
        settings.HelpWriter = Console.Out;
    });

    parser.ParseArguments<StartOptions, FinishOptions>(args)
        .WithNotParsed(ExitWithError)
        .WithParsed(DoSomething);
}

static void DoSomething(object commandObj)
{
    switch (commandObj)
    {
        case StartOptions:
            Console.WriteLine("Start");
            break;
        case FinishOptions:
            Console.WriteLine("Finish");
            break;
    }
}
static void ExitWithError(IEnumerable<Error> errors)
{
    Environment.Exit(1);
}

}
`