#5541 introduced lifecycle hooks into the migrator, but avoids running them if there are no migrations to execute. It returns an empty array from _runBatch in this case, but if there is work to do it returns the result of this._waterfallBatch, which differs: _waterfallBatch returns [0, []] when it has nothing to do.

This causes a confusing error (Uncaught TypeError: Cannot read properties of undefined (reading 'length')) when a user runs migrations from the CLI but no migrations need to be applied (e.g. already at latest / earliest).