fix(gatsby): Prevent errors if Head has root text node

[marvinjude]

Description

Prevent Head from breaking if it contains root level text (text node)

export const Head = () => (
  <>
    Break 
    <title>Head Export</title>
  </>
);

Adding some text like "Break" above will throw errors on trying to access the attribute object on a text node since text nodes have no attribute key

This fix is important for users using a CMS(like WordPress where the text they're trying to pass also contains invalid head elements and root level text(s)

Documentation

https://www.gatsbyjs.com/docs/reference/built-in-components/gatsby-head/

Related Issues

A user reported this issue on discord https://discord.com/channels/484383807575687178/537691356487876624/1009100830261129356