-pool.emitter.on(PoolEvents.full, () => poolFull++)
-pool.emitter.on(PoolEvents.ready, () => poolReady++)
-pool.emitter.on(PoolEvents.busy, () => poolBusy++)
+pool.emitter?.on(PoolEvents.full, () => poolFull++)
+pool.emitter?.on(PoolEvents.ready, () => poolReady++)
+pool.emitter?.on(PoolEvents.busy, () => poolBusy++)