### What this PR does

Fixes #<insert issue number here if relevant>

This is a description of what I've done in this PR, especially explaining choices made to make the reviewer's job easier. If I don't replace this paragraph with an actual description, my PR will probably be ignored.

### Test me

How should reviewers test this? (Hint: If you want to provide a test catalog item, [create a Gist](https://gist.github.com/) of its catalog JSON, add its url and your branch name to this url: `http://ci.terria.io/<branch name>/#clean&<raw url of your gist>` , and then paste that in the body of this PR)

### Checklist

- [ ] There are unit tests to verify my changes are correct or unit tests aren't applicable (if so, write quick reason why unit tests don't exist)
- [ ] I've updated relevant documentation in `doc/`.
- [ ] I've updated CHANGES.md with what I changed.
- [ ] I've provided instructions in the PR description on how to test this PR.