I kept getting this error: Runtime Error: Object reference not set to an instance of an object.

So I deleted all the code that didn't give me that error until I only had this left:

class FatSkyBlueDog(QCAlgorithm):

def Initialize(self):
self.SetStartDate(2021, 4, 19)
self.SetEndDate(2021, 6, 19)
self.SetCash(100000)
self.AddEquity("SPY")

self.CustomUniverse = Universe(self)
self.UniverseSettings.Resolution = Resolution.Daily
self.AddUniverse(self.CustomUniverse.SelectCoarse)
self.AddAlpha(Alpha())

def OnData(self, data):
pass

class Universe():
def __init__(self, algorithm):
self.algorithm = algorithm

def SelectCoarse(self, coarse):
symbol = self.algorithm.Symbol("SPY")
return [symbol]

class Alpha():
def __init__(self):
pass

def Update(self, algorithm, data):
pass

def OnSecuritiesChanged(self, algorithm, changes):
pass

Without the alpha model or the universe model there are no errors. It only breaks when both are there. I don't know what I did. If anyone can tell me how to fix this it would be greatly appreciated.