In the v0 index format, empty descriptions were filled in with boilerplate
text. The v1 index format instead leaves empty descriptions empty, and
lets the various consumers (fdroidclient, web interfaces, etc) decide what
to show. The database and code still assume that the description will not
be null, so instead this ensures there is something in the database, but it
will be an empty string instead of a null. In the future, it would
probably make sense to standardize empty values on null or something.
bc0db92c50