text: Title: Breaks when trying to read an ODIM HDF5 file with missing tilts.
  Body: We had a problem at the BOM with some ODIM HDF5 files. Some scan can be missing some data types.
  
  For example, on one of the file, tilt 10 does not contain reflectivity.  The file itself is valid, but the volume scan does not contain all the data it normally would.
  
  This can happen for lots of reasons but the most common one is that the communications line to the radar was running slowly so some of the moments were dropped.
  
  It would be nice if the reading of ODIM HDF5 files was robust enough to still cope with files like this.  In general, it is not guaranteed that every tilt will always contain the same set of data types.
  
  One solution could be to change l.323 of pyart/aux_io/odim_h5.py to:
  ```python
  try:
      sweep_data = _get_odim_h5_sweep_data(fid[dset][h_field_key])
  except Exception:
      sweep_data = np.zeros((rays_in_sweep, nbins))
      sweep_data = np.ma.masked_where(sweep_data == 0, sweep_data)
  ```