[v0.3.0-rc] Small bug fixes

`Uncaught TypeError: Object prototype may only be an Object or null: undefined`
Was preventing the class from being 'extended', but now that's fixed.

I may update this branch with other small fixes that are similar if I encounter more of them.

Edit: Just read the `CONTRIBUTING.md` for the first time; will make sure to call a branch like this with the bug token next time :+1: