n5-equals handles non existent files/datasets inconsistently

[neptunes5thmoon]

For non existent datasets in hdf5 files n5-equals throws HDF5SymbolTableException. If the file itself doesn't exist the ouput is false.
For n5 files the comparison evaluates to false if one or both of the files/datasets doesn't exist.

The behavior should be consistent for all non-existent files and datasets. I think it would also be desirable to get an output other than false in that case to prevent typos etc.