Null calibration coefficient not caught when trying to save Tilt

[sentry-finland-i9]

Sentry Issue: FERMENTRACK-H

NotNullViolation: null value in column "grav_first_degree_coefficient" violates not-null constraint

  File "django/db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)

IntegrityError: null value in column "grav_first_degree_coefficient" violates not-null constraint
DETAIL:  Failing row contains (1, Green, 15, f, Bridge, 1, null, 1, 70, tiltbridgeGreen, ff537373-4343-46eb-bf66-66a500df8bda).

(14 additional frame(s) were not displayed)
...
  File "app/decorators.py", line 25, in _wrapped_view
    return view_func(request, *args, **kwargs)
  File "gravity/views_tilt.py", line 73, in gravity_tilt_coefficients
    sensor.tilt_configuration.save()