NullErr
const class NullErr : Err
NullErr indicates an attempt to dereference null. It is often raised when attempting to access an instance field or method on a null reference. It may also be thrown when a parameter is expecting a non-nullable argument and null is passed.
Construct with specified error message and optional root cause
new make(Str msg, Err? cause)
Construct with specified error message and optional root cause.