[interp] [wasm] assert on null dereference of struct array

[Suchiman]

Steps to Reproduce

1. Run this program with interpreter on wasm (desktop unchecked)

public class Program
{
    public static void Main(string[] args)
    {
        TestStruct[] frames = null;
        _ = frames[0];
    }
}

public struct TestStruct
{
}

Current Behavior

WASM: * Assertion at /mnt/jenkins/workspace/test-mono-mainline-wasm/label/ubuntu-1804-amd64/mono/mini/interp/interp.c:902, condition `m_class_get_rank (ac) >= 1' not met blazor.webassembly.js:1:32098
uncaught exception: abort(). Build with -s ASSERTIONS=1 for more info.

Expected Behavior

should throw NullReferenceException.

On which platforms did you notice this

[ ] macOS
[ ] Linux
[x] Windows (wasm)

Version Used:
c8d59d1