Fix selecting and deleting fields from zero-chunked ext-array

[hombit]

Another annoying edge case

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.25%. Comparing base (cb5b36d) to head (d650fd8).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #373      +/-   ##
==========================================
- Coverage   98.26%   98.25%   -0.02%     
==========================================
  Files          19       19              
  Lines        1906     1891      -15     
==========================================
- Hits         1873     1858      -15     
  Misses         33       33              

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[github-actions]

Before [cb5b36d]	After [725e78b]	Ratio	Benchmark (Parameter)
52.2±2ms	47.4±0.1ms	~0.91	benchmarks.ReassignHalfOfNestedSeries.time_run
176M	179M	1.02	benchmarks.ReadFewColumnsHTTPS.peakmem_run
11.9±0.2ms	12.0±0.3ms	1.01	benchmarks.NestedFrameAddNested.time_run
1.92±0.03s	1.93±0.04s	1.01	benchmarks.ReadFewColumnsHTTPS.time_run
250M	250M	1.00	benchmarks.AssignSingleDfToNestedSeries.peakmem_run
135M	135M	1.00	benchmarks.CountNestedBy.peakmem_run
65.6±0.6ms	65.4±0.3ms	1.00	benchmarks.CountNestedBy.time_run
101M	101M	1.00	benchmarks.NestedFrameAddNested.peakmem_run
106M	106M	1.00	benchmarks.NestedFrameQuery.peakmem_run
105M	105M	1.00	benchmarks.NestedFrameReduce.peakmem_run

Click here to view all benchmarks.

[dougbrn]

LGTM!