fix(rust): unable to read delta table when table contains both null and non-null add stats

[yjshen]

Description

To fix the issue when a delta table contains add action with stats_parsed: null.

As shown in the test case, 001.json contains an Add action with stats, while 002.json contains an Add action with stats_parsed: null, before this fix, it will complain:

Arrow { source: InvalidArgumentError("all columns in a record batch must have the same length") }

The issue is that the array for num_records has two values, while for other stats such as null_count, the None value is filtered out by flat_map, so there is only one value in the array.

Related Issue(s)

closes #2477

Documentation