Who would've thought?
`:` means or empty, so:
```sh
VAR=
echo "${VAR-default}" # prints 'default'
VAR=''
echo "${VAR-default}" # prints ''
VAR=''
echo "${VAR:-default}" # prints 'default'
```
;-; nothing wants to work
This allows us to analyze the report more easily. There is experimental
support for comparing against a base report, but we don't expose that
functionality to the action.
