Bugfix: pending waiter

[DnlLrssn]

Checklist

• [x] tests added
• [x] commits conform to the Commit message format
• [ ] documentation updated

Squash commit message

Fixes bug where something added to state.pending after emptying, but before emptying of resthandler.pending would not wait as expected.

Info

Optional informative text (not to be included in commit message) relevant to reviewers.