@exetico @Curtis_Kephart After some digging it turns out that the issue you both reported will not occur if you run Discourse on any commit after (and including) this one
https://github.com/discourse/discourse/commit/92b7fe4c62094275c5dd09b1f3dac5c5cbcad1c0
If you’re running Discourse on an older commit you’ll get this error
Unexpected error while indexing post for search : PG::NotNullViolation: ERROR: null value in column “private_message” violates not-null constraint
The plugin (unchanged) works as expected on the latest version of Discourse.