Empty document errors with: "expected ..."

[wrdls]

A yaml file like this

a: b
---
# some comment
---
b: c
d: 123

generates the following error:

❯ dprint fmt test.yaml
Error formatting test.yaml. Message: parse error at line 5, column 2
  |
5 | b: c
  |  ^
expected `...`
Had 1 error formatting.

These kind of documents are pretty common in Kubernetes yaml files generated by Helm, where range and/or if statements leads to empty documents.