NullReferenceException when passing null for a byte[]

[iablaauw-MS]

Describe the bug
Using a CsWinRT projected type, constructing it and passing null causes an exception to come from inside the generated cswinrt code.

It appears that somewhere in MarshalBlittable null isn't handled properly.

To Reproduce

• Use Win2D in a new project
• new Microsoft.Graphics.Canvas.Effects.PixelShaderEffect((byte[])null))
• Causes a NullReferenceException

Expected behavior
An argument exception from inside of Win2D complaining about the null being passed in.

Version Info

• CsWinRT version: 1.3.0
• .NET 5
• Windows SDK: 10.0.18362.0

Additional context