Fix failure to save files when split table contains no data

[jleibs]

Fixes:

• Saving through the file menu is broken on 0.5.0 #2005

What

The root cause of the problem was arrow failing to concatenate if there was no data in the table. This checks for that condition and bypasses the serialize_data_column call all together.

Added new test that fails with same conditions:

test data_store_dump_empty_column ... FAILED

failures:

---- data_store_dump_empty_column stdout ----
thread 'data_store_dump_empty_column' panicked at 'called `Result::unwrap()` on an `Err` value: Arrow(InvalidArgumentError("concat requires input of at least one array"))', crates/re_arrow_store/tests/dump.rs:296:26

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)

PR Build Summary: https://build.rerun.io/pr/2007

[emilk]

It would be nice with a regression test of this too, if it is not too much trouble.

I think we should merge this into main first, then cherry-pick it into a 0.5.1 branch. This will ensure it ends up correctly in the changelog (and that it gets main-lined quicker)

[jleibs]

Ok, rebased to main so we can cherry-pick back to hotfix.
I could definitely use a hand from @teh-cmc figuring out how to actually trigger this in a regression test.
I introduced a unit test that replicates the problem, but could definitely use a sanity check from @teh-cmc
I think this has something to do with introducing a table that starts with an element that then gets split?

[emilk]

I think we should crash on errors in tests, no?

here and below

Suggested change

	store.insert_table(&table).ok();
	store.insert_table(&table).unwrap();