Index issue with synced-cron

[fumbleforce]

Hey there,
After updating synced-cron, we were getting 100% cpu usage due to this query made by synced-cron, which was not an issue before. I don't think the query is well-formed, $exists: false is not indexable. Maybe having a default false value would help, as well as a specific index on this.

[fumbleforce]

Guess I should also clean up my cronHistory, hehe. Not like we need the docs.