I think 'Dereference of a possibly null reference' may have to join 'object not set to a reference of an object' as my least loved and most unhelpful error/warning message ever!
@CodeBunTes I don't know your context, but this warning generally should help you improve the quality of your code by detecting missing null checks.
So 'Dereference of a possibly null reference' at compile time may lead to 'object not set to a reference of an object' at runtime.