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PR Title
Add null check on Task, Task, ValueTask, ValueTask

PR Description
Prevent returning null from Map{Verb}(string, Delegate), adding a null check (that throw an exception) on Task, Task<IResult>, ValueTask, ValueTask<IResult>

https://github.com/wcontayon/AspNetCore/blob/cae7c582b6aec95c780897c089cc6d3e936842d7/src/Http/Http.Extensions/src/RequestDelegateFactory.cs#L830-L852

Addresses #32865