MissingReferenceException on StartCoroutine() calls.

Questions & Answers
1

when defeating enemies, I want to adjust the lighting intensity. I want the lighting to adjust over time and not snap from one value to another, so I’m using a coroutine.
for some reason, the line starting the coroutine return a MissingReferenceException for an instance of the class that contains the coroutine.
this is the code:

void onPollutionDwindled(float i_FogDwindled)
    {
        float fog = Mathf.Clamp(i_FogDwindled, 0.1f, 0.8f);
        currentIntensity = fog;


        float delta = currentIntensity - light.intensity;
		StartCoroutine(updateLight());

		IEnumerator updateLight()
		{
            int numberOfSteps = 3;
            float step = delta / numberOfSteps;
            for(int i = 0; i < numberOfSteps; i++)
			{
                light.intensity += step;
                light.intensity = Mathf.Clamp(light.intensity, 0.1f, 0.7f);
				yield return null;
			}
		}
    }

This is the error message:

MissingReferenceException: The object of type 'LightingManager' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object.

LightingManager is the class the contains OnFogDwindled

normally I would say that I had just forgotten to instantiate said instance, but the weird thing is that if I change this:

StartCoroutine(updateLight());

To this:

updateLight();

(and of course adjust the function return type to void and comment out the the yield statement), everything works fine, except the fact that the light does not change gradually, which is to be excpeted.

why would a coroutine cause this behaviour?

P.S: If it matters, OnFogDwindled listens to an event in a different class and invoked when an enemy is defeated.

2

Could be the mentioned event causing the problem, there could be listeners of the event that has been destroyed, i’ve notice that events can sometimes throw errors from weird places.

Make sure that all objects listening to the event unregisters when disposed.

Public void OnDestroy(){
     YourEventHandler.YourEvent -= this.YourDelegateListenerMethod();
}