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

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(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 errors)
{
Environment.Exit(1);
}
}
`

Start with the Parser.ParseArguments call shown in the issue and reproduce the behavior using DefaultVerb.exe foo with the default verb enabled. Trace how an unrecognized verb is handled when a default exists, then verify that the invalid input reaches the error path rather than DoSomething or the default verb.

Written by the indexing model from the issue text.