[BUG] common.GetShare potential divide by zero error

When calculating shares in a total pool, the common.GetShare method is used. Although this method checks that the part and total fields provided are non-zero to prevent a division by zero, it performs two Quo operations, with the result of one being used as the denominator in another. In the event that the inner Quo call results in zero, this will result in a division-by-zero panic.