When setting up the mutation observer the code assumes the `<body>` tag is available, which when loading via the head it isn't. https://github.com/guardian/iframe-messenger/blob/master/src/iframeMessenger.js#L139
When setting up the mutation observer the code assumes the
<body>tag is available, which when loading via the head it isn't.https://github.com/guardian/iframe-messenger/blob/master/src/iframeMessenger.js#L139