It means you’re trying to apply an event whilst you don’t have a UnitOfWork.
More code specific, you’re calling either
AggregateLifecycle.isLive() or 'AggregateLifecycle.markDeleted()` whilst you don’t have a UnitOfWork started, which probably means you’re calling one of those functions outside of an aggregate.
However, a code example would work better to tell you what’s going wrong.
Could you share a snippit of code of the ‘command and event handlers defined’?