Fix GetWrappedType implementation(s) to not return null

[Metadorius]

Motivation for this change:
I tried to resolve IContainer through third-party Splat.DryIoc dependency resolver in my app (bad practice but WinForms is a bad practice by itself, so eh). It errored with a NullReferenceException here (none of the params were generic):

DryIoc/src/DryIoc/Container.cs

Lines 5072 to 5077 in e6a4e33

	var requiredItemType = container.GetWrappedType(itemType, details.RequiredServiceType);
	var items = container.GetServiceRegisteredAndDynamicFactories(requiredItemType) // todo: @bug check for the unregistered values
	.Map(requiredItemType, (t, x) => new ServiceRegistrationInfo(x.Value, t, x.Key));
	if (requiredItemType.IsClosedGeneric())

Upon further inspection I found out that the methods shouldn't ever return null, according to documentation:

DryIoc/src/DryIoc/Container.cs

Line 14054 in e6a4e33

/// <returns>Unwrapped service type in case it corresponds to registered generic wrapper, or input type in all other cases.</returns>

And here:

DryIoc/src/DryIoc/Container.cs

Line 14059 in e6a4e33

/// Otherwise, method returns the input <paramref name="serviceType"/>.</summary>

Yet one of the branches was seemingly erratically returning null, so I fixed that.

[dadhi]

Thanks, I will look a bit later.

[Metadorius]

Any updates on that? It should be a pretty small oversight, as the documentation (and code usage) assumes the methods will never return null, and it clearly looks like an oversight that it returns null in one case when in another it returns the initial type properly. It's breaking in some of the usage scenarios of the container, particularly resolving the container through Splat which calls the method in question.

[dadhi]

I am on vacation till 8th of March, so I will look when I have time.

[dadhi]

Hi, thanks for PR, merging.

[dadhi]

@Metadorius The v5.3.4 containing the PR is out. Thanks!