manual provider appears twice in boilerplate config

I noted that "juju init" creates a boilerplate config where the manual provider appears twice.

This can be tracked back to juju-core/provider/manual/provider.go, lines 19 & 20 where the manual provider is registered twice, once with the name "null" and once with the name "manual", but referring to the same provider.
Hence, BoilerplateConfig() is called twice on the same variable (manualProvider{}), and its boilerplate code appears twice. In that boilerplate code "manual" is hardcoded.

That was on revno 2290 by the way.