Raise an error if the whole mask is land? #64
Description
Currently the tool will accept a mask consisting only of land (e.g., test_0.nc). However, it isn't at all obvious what the expected behaviour should be for such a case.
Perhaps we should have the tool raise an error (or at least a warning) if it is provided with a mask that is land-only. After all, domain_decomp is designed to produce decompositions for nextSIM-DG and nextSIM-DG wouldn't work for a domain with only land.