convert_msv2_to_processing_set pointing KeyError exception

[pford]

xradio version: 0.0.38

convert_msv2_to_processing_set(with_pointing=True) raises an exception for msv2s where antenna ids are missing from the main table.

An example is a VLA casaguides tutorial calibrated MS (1.4GB) which contains VLA-SgrA-Sband-Aconfig.ms, VLA-SgrA-Sband-Bconfig.ms, and VLA-SgrA-Sband-Cconfig.ms. All three MSs get the conversion exception; the Aconfig MS has 26 antennas (id 0-25) defined in the ANTENNA and POINTING tables but antenna id 12 is missing from the main table, so the selection fails:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/groot/casa/github/xradio/src/xradio/vis/convert_msv2_to_processing_set.py", line 104, in convert_msv2_to_processing_set
    convert_and_write_partition(
  File "/home/groot/casa/github/xradio/src/xradio/vis/_vis_utils/_ms/conversion.py", line 902, in convert_and_write_partition
    pointing_xds = create_pointing_xds(
                   ^^^^^^^^^^^^^^^^^^^^
  File "/home/groot/casa/github/xradio/src/xradio/vis/_vis_utils/_ms/msv4_sub_xdss.py", line 320, in create_pointing_xds
    "antenna_name": ant_xds_name_ids.sel(
                    ^^^^^^^^^^^^^^^^^^^^^
  File "/home/groot/anaconda3/envs/gui_env/lib/python3.11/site-packages/xarray/core/dataarray.py", line 1614, in sel
    ds = self._to_temp_dataset().sel(
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/groot/anaconda3/envs/gui_env/lib/python3.11/site-packages/xarray/core/dataset.py", line 3091, in sel
    query_results = map_index_queries(
                    ^^^^^^^^^^^^^^^^^^
  File "/home/groot/anaconda3/envs/gui_env/lib/python3.11/site-packages/xarray/core/indexing.py", line 190, in map_index_queries
    results.append(index.sel(labels, **options))
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/groot/anaconda3/envs/gui_env/lib/python3.11/site-packages/xarray/core/indexes.py", line 784, in sel
    raise KeyError(f"not all values found in index {coord_name!r}")
KeyError: "not all values found in index 'antenna_id'"

[Jan-Willem]

@pford I have pushed a fix to the branch (245-convert_msv2_to_processing_set-pointing-keyerror-exception).

[pford]

This branch worked for the VLA-SgrA msv2s as well as another failing VLA ms. Thanks!