Morpho

Morpho fails with an error when entering a new table description without
pointing at an object. One should be able to provide a metadata-only
description of the table (we'll eventually want to use this feature to configure
data entry forms).

To reproduce:

Package editor -> Add -> Import Data
Leave data field blank
choose "manually enter fiel descriptions
enter metadata for the entity and attributes
when you hit "Next" it fails with the error:
"Error saving file: NULLDATAFILE (No such file or directory)"

Instead, it should add the entity and attribute metadata files, and the table
editor should change the "View data" button to "Associate data" in order to
allow the user to come back later and associate the data file with the metadata
description that was produced. At that point in time the eml-physical
description would be added.