在设备上运行时不会出现SKEmitterNode

I've been learning to use Spritekit in Swift these past few days using the Hacking With Swift Tutorials (Specifically Project 23). I was learning how to use SKEmitterNodes however they don't ever seem to appear. On runtime, the screen is a blank grey color that runs at 1 fps with 1 node on screen (supposedly the SKEmitterNode). I've tried changing the zPosition of the node but it doesn't seem to have any effect. Oddly, SKSpriteNodes and SKLabelNodes appear just fine. I cleaned the project and got rid of the "Hello World" in the GameScene.sks so I know its not anything from the default project. I've googled around extensively for an answer to this question but I've come up blank. Below is the offending code. I've been learning to use Spritekit in Swift th