Gatsby Sitemap plugin build issue

[DavidWells]

From this commit when sitemap plugin enabled https://github.com/DavidWells/new-site/commit/ae77b2b5e447ecf07416e5d67c252be4624f6b6f

The build fails with this error:

There is a siteUrl defined... https://github.com/DavidWells/new-site/commit/ae77b2b5e447ecf07416e5d67c252be4624f6b6f#diff-b9e136416b90437fa1dac910280b45fcR8

Unclear on why "Protocol is required" error is throwing.

The error vanishes if I disable the sitemap plugin and try the build again