Doc needs more info on null data

For instance, if I use a Where<>() clause and it finds no matching items in a collection, does it return null or an empty collection? If I chain a .ToArray() on to the Where() clause for immediate evaluation will it throw a null argument exception or will it just return null or the empty collection?

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* ID: 90e254e7-ea82-c901-3b99-fea65c947aac
* Version Independent ID: 5302bfde-2fa0-4275-e38a-4fadbf5fc1c3
* Content: [Enumerable.ToArray(IEnumerable<TSource>) Method (System.Linq)](https://docs.microsoft.com/en-us/dotnet/api/system.linq.enumerable.toarray?view=netframework-4.7.2)
* Content Source: [xml/System.Linq/Enumerable.xml](https://github.com/dotnet/dotnet-api-docs/blob/master/xml/System.Linq/Enumerable.xml)
* Product: **dotnet-api**
* GitHub Login: @dotnet-bot
* Microsoft Alias: **dotnetcontent**