Mask out planes with NaN beams

[keflavich]

No description provided.

[keflavich]

I have a problem here: Why did this fail:
https://github.com/keflavich/spectral-cube/blob/426400624cf949aea8053ae7232265d1b07c4348/spectral_cube/spectral_cube.py#L2450

but this worked:
https://github.com/keflavich/spectral-cube/blob/master/spectral_cube/tests/test_masks.py#L398

as far as I can tell, they're the same code, but the first instance resulted in deep failures while the second has always worked.

EDIT:
specifically, the failure mode looks like this:

    def _include(self, data=None, wcs=None, view=()):
>       result_mask = self._mask[view]
E       IndexError: index 1 is out of bounds for axis 2 with size 1

[coveralls]

Coverage decreased (-0.08%) to 72.541% when pulling 4264006 on keflavich:check_bad_beams into c10395f on radio-astro-tools:master.

[coveralls]

Coverage increased (+0.08%) to 72.695% when pulling f518421 on keflavich:check_bad_beams into c10395f on radio-astro-tools:master.

[keflavich]

@e-koch @low-sky @astrofrog any of you up for reviewing this?

[coveralls]

Coverage increased (+0.08%) to 72.695% when pulling 5c3579b on keflavich:check_bad_beams into c10395f on radio-astro-tools:master.