Check column exists in NestedFrame.__setitem__

[hombit]

Fixes bug introduced during the changes to support non-unique indices.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.40%. Comparing base (96503cd) to head (1f86e14).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #173   +/-   ##
=======================================
  Coverage   99.40%   99.40%           
=======================================
  Files          14       14           
  Lines        1003     1004    +1     
=======================================
+ Hits          997      998    +1     
  Misses          6        6           

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[github-actions]

Before [96503cd] <v0.3.0>	After [028c457]	Ratio	Benchmark (Parameter)
22.4±0.6ms	23.0±0.8ms	1.03	benchmarks.AssignSingleDfToNestedSeries.time_run
31.3±8ms	31.8±5ms	1.02	benchmarks.ReassignHalfOfNestedSeries.time_run
266M	266M	1	benchmarks.AssignSingleDfToNestedSeries.peakmem_run
88.4M	88.2M	1	benchmarks.NestedFrameAddNested.peakmem_run
9.20±0.1ms	9.18±0.1ms	1	benchmarks.NestedFrameAddNested.time_run
93.4M	93.2M	1	benchmarks.NestedFrameQuery.peakmem_run
7.91±0.1ms	7.92±0.1ms	1	benchmarks.NestedFrameQuery.time_run
91.8M	91.8M	1	benchmarks.NestedFrameReduce.peakmem_run
285M	285M	1	benchmarks.ReassignHalfOfNestedSeries.peakmem_run
1.61±0.02ms	1.53±0.01ms	0.95	benchmarks.NestedFrameReduce.time_run

Click here to view all benchmarks.