operator + method Null safety
- dynamic other
 
Implementation
double operator +(other) => isNotNull
    ? value! + other!
    : throw EmpirePropertyNullValueException(
        StackTrace.current, propertyName, runtimeType);
double operator +(other) => isNotNull
    ? value! + other!
    : throw EmpirePropertyNullValueException(
        StackTrace.current, propertyName, runtimeType);