Replace "0"s made in the unwrapping output with the original wrapped phase value

[scottstanie]

Since we don't want to make it impossible for a better unwrapping job, we'd rather keep the original wrapped phase where the unwrapper gave up.

• [ ] Make sure we reset all data originally in the interferogram (both masked for unwrapping, and badly unwrapped areas)
• [ ] Ensure that the edges haven't gotten slightly off of the nodata value. Every frame should be nans around the outside, and something nonzero inside
• ~Make sure we have some clear mask layer which says "we think you should probably ignore these areas"~