bug in add method

[AndroidDesigner]

I think there is a bug in add method.
suppose call this method in another class as:
mJalaliCalendar.add(Calendar.MONTH,-1);
and suppose MONTH is "FARVARDIN".
This result in : "amount = -1" and equally amount%12 = -1.
so array index is negative!

[WhiteEglantine]

I also faced this bug and fixed it:
if (field == MONTH) {
int month;
if (amount < 0) {
add(YEAR, (amount / 12)-1);
month = get(MONTH) + 12 + amount;
} else {
amount += get(MONTH);
add(YEAR, amount / 12);
month = amount % 12;
}
super.set(MONTH, month);
if (get(DAY_OF_MONTH) > jalaliDaysInMonth[month]) {
super.set(DAY_OF_MONTH, jalaliDaysInMonth[month]);
if (get(MONTH) == 11 && isLeepYear(get(YEAR))) {
super.set(DAY_OF_MONTH, 30);
}
}
complete();
}