fix(logger): let empty entries inherit parent indentation level

[eysi09]

With this change, empty log entries inherit their parent's indentation level. An alternative would be to set the indentation level to zero so that all empty entries—including nested ones—get aligned with the root nodes. I could swing either way (it's a one liner fix), but the former feels a bit more consistent.

So currently, this:

const root = garden.log.info("root")
const empty = root.info()
empty.setState("same level as root")
const deep = empty.info("deep")
const deepEmpty = deep.info()
deepEmpty.setState("same level as deep")

prints this:

root
same level as root
    deep
    same level a deep