message json data is missing on Signal Desktop 7.42 for Windows

[aheilbut]

Exporting doesn't work from the latest version of Desktop on Windows (and using #163 )-- there is no output for any chats.

If you specify --include-empty, then sigexport will make folders for all chats, but it's empty.

The problem is that the json field is not populated for messages in the database on Windows -- even though the data is actually all there, but broken out into the fields of the table.

Potential workaround is to pull the field values from the individual database fields rather than from the json, but this may be a bug in Signal Desktop itself on windows, as on the Mac desktop version, the json field does seem to have all the data for all messages.

update: This seems to be a deliberate change, see: signalapp/Signal-Desktop@630a1fc.
I'm a little confused why things are still OK on the mac 7.42