_executeCallback(result, callback) {
        if (!AutoNumericHelper.isNull(callback) && AutoNumericHelper.isFunction(callback)) {
            callback(result, this);
        }
    }
Execute the given callback function using the given result as its first parameter, and the AutoNumeric object as its second.

@param {number|string|Array|null} result
@param {function|null} callback If a callback is passed, then the result is passed to it as its first argument, and the AutoNumeric object has its second
@private