presto-main/src/main/java/io/prestosql/operator/aggregation/DecimalAverageAggregation.java/DecimalAverageAggregation/initializeIfNeeded
class DecimalAverageAggregation:    private static void initializeIfNeeded(LongDecimalWithOverflowAndLongState state)
    {
        if (state.getLongDecimal() == null) {
            state.setLongDecimal(UnscaledDecimal128Arithmetic.unscaledDecimal());
        }
    }