Null ref when attempting to assign null to value-type collections

[layomia]

An example is ImmutableArray which is a struct. Discovered when fixing https://github.com/dotnet/corefx/issues/41598.

Should throw JsonException instead.

[layomia]

There's also an issue with nullable value-type collections. From @ahsonkhan in dotnet/corefx#42420 (comment):

As an aside, looks like nullable ImmutableArray breaks:

Console.WriteLine(JsonSerializer.Deserialize<ImmutableArray<DateTime>?>("null") == null);

Unhandled exception. System.ArgumentNullException: Value cannot be null.
   at System.RuntimeType.MakeGenericType(Type[] instantiation)

[layomia]

Closing as duplicate of #1037.