Fix: allow empty RecordArrays in ak.to_layout

[agoose77]

Fixes #1578

[codecov]

Codecov Report

Merging #1581 (fb64999) into main (9e17f29) will decrease coverage by 0.01%.
The diff coverage is 35.13%.

Impacted Files	Coverage Δ
src/awkward/_v2/_connect/cuda/__init__.py	0.00% <0.00%> (ø)
src/awkward/_v2/_connect/numexpr.py	88.40% <0.00%> (ø)
src/awkward/_v2/_connect/pyarrow.py	88.46% <0.00%> (ø)
src/awkward/_v2/contents/bytemaskedarray.py	88.82% <0.00%> (ø)
src/awkward/_v2/contents/indexedarray.py	73.83% <0.00%> (ø)
src/awkward/_v2/contents/indexedoptionarray.py	89.14% <0.00%> (ø)
src/awkward/_v2/contents/listoffsetarray.py	81.85% <0.00%> (ø)
src/awkward/_v2/contents/unionarray.py	86.27% <0.00%> (ø)
src/awkward/_v2/numba.py	93.47% <0.00%> (ø)
src/awkward/_v2/operations/ak_from_avro_file.py	66.66% <0.00%> (ø)
... and 6 more

[blink1073]

LGTM!

[jpivarski]

That fix looks correct to me, also, but the tests are failing because some CI nodes don't have pyarrow installed. You just need to put a

pyarrow = pytest.importorskip("pyarrow")

at the top of the test file.

And then squash-and-merge when it works; this seems to have been an easy fix!