Summary:
Fixes T5273. Two issues:
- If a JX.Resource callback throws, we keep running it. Instead, make sure it gets cleaned up before raising an exception.
- The countdown timer script doesn't recover gracefully if the node has been removed from the document by the time it runs. Instead, just bail if we can't find the countdown.
Test Plan: Dumped `{Cxyz}` into a preview and got a countdown.
Reviewers: yungsters
Reviewed By: yungsters
Subscribers: epriestley
Maniphest Tasks: T5273
Differential Revision: https://secure.phabricator.com/D9399
d06679a021