`ClipboardItem` constructor should throw when `items` are empty

[mbrodesser]

const c = new ClipboardItem([]);

Chrome and Firefox both throw a TypeError. The spec doesn't cover this case.

CC @snianu Keeping this separate from #158 to not widen its scope.

[snianu]

@mbrodesser Ah you are right. It should throw a TypeError. I can add it to the spec if you want, but if this needs further discussion then we can do this in a separate PR.

[mbrodesser]

@snianu let's pull #158 first. This is a minor issue.

[EdgarChen]

Now spec throws TypeError when items is empty after #158, i.e.

The new ClipboardItem(items, options) constructor steps are: If items is empty, then throw a TypeError.

Could we close this?

[snianu]

I think we can close this. Thanks for the reminder!