presto-main/src/main/java/io/prestosql/operator/aggregation/arrayagg/SingleArrayAggregationState.java/SingleArrayAggregationState/isEmpty
class SingleArrayAggregationState:    @Override
    public boolean isEmpty()
    {
        if (blockBuilder == null) {
            return true;
        }
        verify(blockBuilder.getPositionCount() != 0);
        return false;
    }