usability request: improve error message when missing requirement (when no verbs/arguments match)

We've used your library a long time, it's very helpful thanks.

I wanted to request that you consider checking for linq errors and not throwing an exception but providing an error.

The best example is this one which I am seeing a lot ( nuget version: 2.8.0 )

System.InvalidOperationException : Sequence contains no elements

This has happened both for coding errors (copying an option class and forgetting to rename verb) but also for user/usage errors, when some arguments don't match.

This is coming from Linq, it would be more helpful to diagnose them if you could check for requirements prior to parsing a verb or argument and return relevant error.

Start by tracing the LINQ path that raises “Sequence contains no elements” during verb or argument parsing. Review how missing requirements and unmatched arguments are currently handled, then define and test a relevant diagnostic error for both cases instead of the exception.

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