Unable to share attachments from other applications

[distefam]

Describe the bug
Sharing attachments via other applications opens an unusable share sheet.

To Reproduce
Steps to reproduce the behavior:

1. Go to photos
2. Share a photo
3. Select Snikket as a destination application
4. Observe empty share sheet

Expected behavior
Share sheet should allow user to select at least one contact with whom to share the given photo.

Screenshots
Here is a short screen recording of the observed behavior:
https://user-images.githubusercontent.com/65571/109175492-d84f5200-7753-11eb-9f35-a31a5eb345c1.mp4

[mwild1]

This issue is currently on hold. There is a PR #56 to fix the empty accounts list. However that fix reveals other issues - notably that text/attachments shared this way are sent unencrypted.

The share extension runs as a separate process, and if the main process is running, it may not be able to reliably read/write the database that stores the OMEMO sessions. There are plans to fix this upstream (Siskin 7.0).

For now we will disable sharing from other apps (#64) and revisit it further down the road.