Merge "Return zero delta when delta is not computed"

template <class T>

const T& MultiStateCounter<T>::updateValue(const T& value, time_t timestamp) {

    T* returnValue = &emptyValue;

    // If the counter is disabled, we ignore the update, except when the counter got disabled after

    // the previous update, in which case we still need to pick up the residual delta.

    if (isEnabled || lastUpdateTimestamp < lastStateChangeTimestamp) {

        if (lastUpdateTimestamp >= 0) {

            if (timestamp > lastUpdateTimestamp) {

                if (delta(lastValue, value, &deltaValue)) {

                    returnValue = &deltaValue;

                    time_t timeSinceUpdate = timestamp - lastUpdateTimestamp;

                    for (int i = 0; i < stateCount; i++) {

                        time_t timeInState = states[i].timeInStateSinceUpdate;

    }

    lastValue = value;

    lastUpdateTimestamp = timestamp;

    return deltaValue;

    return *returnValue;

}

template <class T>