Fix shift_indexes_in_buckets by going through the whole m_buckets_data instead of finding back the bucket through m_values
shift_indexes_in_buckets was trying to find back a bucket through m_values but as it modifies the indexes during the iteration, there's a risk of having two buckets with the same index for which we can't reliably know which one still need a shift by delta.
Fix shift_indexes_in_buckets by going through the whole m_buckets_data instead of finding back the bucket through m_values
shift_indexes_in_buckets was trying to find back a bucket through m_values but as it modifies the indexes during the iteration, there's a risk of having two buckets with the same index for which we can't reliably know which one still need a shift by delta.
Fix issue #38