Fix bonemeal alias registration by conditionally registering flora alias only when bonemeal mod is present

[Pivert]

WorldEditAdditions is trying to register an alias from bonemeal to flora, but the bonemeal command doesn't exist (because the bonemeal mod isn't detected). However, the alias registration is still proceeding and this is likely creating a command definition with a nil source.

[sbrl]

You're trying to merge into main, but could you edit your merge to be against the dev branch instead please?