Summary:
For fg-masking depth, we assumed np.array but passed a Tensor; for defining the default depth_mask, vice versa.

Note that we change the intended behaviour for the latter, assuming that 0s are areas with empty depth. When loading depth masks, we replace NaNs with zeros, so it is sensible. It is not a BC change as that branch would crash if executed. Since there was no reports, I assume no one cared.

Reviewed By: bottler

Differential Revision: D47403588

fbshipit-source-id: 1094104176d7d767a5657b5bbc9f5a0cc9da0ede