Behavior of UInt8Array.fromArray(x) - where x evaluates to [null]

Not sure if this could be labeled as undefined behavior, or can be classified as a bug.
Posting so you can take a look at it.

Code:

```haxe
var intArray = ''.split(' ').map(function(part):Int {
return Std.parseInt(part);
});
trace("intArray: " + intArray);
var u8Array = UInt8Array.fromArray(intArray);
trace("u8Hex: <" + u8Array.view.buffer.toHex() + ">");
```

Output:

| target | intArray | u8Hex |
|--------|----------|-----------|
| js | [null] | <00> |
| python | [null] | Exception |
| eval | [null] | Exception |
| cs | [0] | <00> |
| cpp | [0] | <00> |
| hl | [0] | <00> |
| swf | [0] | <00> |

Now, I'd lean towards how python and eval behave here - throwing an exception at runtime - although they diverge from js!
But there's still the problem that the behavior is inconsistent across targets.

Compiled with 4.0.0-preview.5