fix: No events returned when one of many orgs in filter does not exist

[tomking2]

What does it do?

Discovered that when using the search_index endpoint (or filtering through UI), if you pass a list of organisations in the org parameter, and at least one of the orgs does not exist (either by ID, UUID or Name), then no results are returned. It did not matter if other orgs provided in the parameter exist.

To replicate:
The following search returns a result:

pm.search_index(org=["CIRCL"], limit=1)

The following does not:

pm.search_index(org=["CIRCL", "CIRCL_____MISSING"], limit=1)

Fixed by handling where at least one org was found, and also skipping including an empty $test in the conditions (for code cleanup)

Questions

• Does it require a DB change?
• Are you using it in production?
• Does it require a change in the API (PyMISP for example)?