Error in HORIZONS ephemeris filtering (TypeError: Cannot convert fill_value ? to dtype bool)

[talister]

View details in Rollbar: https://rollbar.com/LCO/NEOexchange/items/154/

Traceback (most recent call last):
  File "/opt/lcogt-python36/lib/python3.6/site-packages/django/core/handlers/base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/var/www/apps/neoexchange/core/plots.py", line 196, in make_visibility_plot
    vis_file = plot_hoursup(ephem, site_code, add_rate=to_add_rate, alt_limit=tel_alt_limit, base_dir=base_dir)
  File "/var/www/apps/neoexchange/photometrics/obsgeomplot.py", line 331, in plot_hoursup
    visible_dates, hours_visible = determine_hours_up(ephem_ca, site_code, dbg)
  File "/var/www/apps/neoexchange/photometrics/obsgeomplot.py", line 299, in determine_hours_up
    & (ephem_ca['solar_presence'] != 'C') & (ephem_ca['solar_presence'] != 'N')]
  File "/opt/lcogt-python36/lib/python3.6/site-packages/astropy/table/column.py", line 991, in _compare
    result = getattr(super(), op)(other)
  File "/opt/lcogt-python36/lib/python3.6/site-packages/astropy/table/column.py", line 359, in __array_finalize__
    super().__array_finalize__(obj)
  File "/opt/lcogt-python36/lib/python3.6/site-packages/numpy/ma/core.py", line 3063, in __array_finalize__
    self._fill_value = _check_fill_value(self._fill_value, self.dtype)
  File "/opt/lcogt-python36/lib/python3.6/site-packages/numpy/ma/core.py", line 474, in _check_fill_value
    raise TypeError(err_msg % (fill_value, ndtype))
TypeError: Cannot convert fill_value ? to dtype boolTraceback (most recent call last):
  File "/opt/lcogt-python36/lib/python3.6/site-packages/numpy/ma/core.py", line 468, in _check_fill_value
    fill_value = np.array(fill_value, copy=False, dtype=ndtype)
ValueError: invalid literal for int() with base 10: '?'

[talister]

This is being generated by an interaction between astropy >=3.2.2 and a numpy bug as I filed back in October 2019: astropy/astropy#9374