When editing detection zones, snapshots initially load, but are replaced with a plain grid after 10 seconds #622

When editing zones for a stream, initially the snapshot image will initially load correctly. It then disappears within 10 seconds and is replaced with a grid and the notice "Snapshot unavailable - drawing on grid background".

Root Cause

The setTimeout() closure at ZoneEditor.jsx:95 captures imageLoaded when the closure is created. When setImageLoaded() is called, a new render is made, but the closure is not replaced. imageLoaded evaluates to false and the snapshot gets removed.

Possible Fixes

1. Cancel the timeout (clearTimeout()) when the image successfully loads
2. Modify the closure and/or utilize useEffect to check the current value of imageLoaded at the time that the closure runs -- see examples in https://stackoverflow.com/questions/73697416/react-stale-usestate-value-in-closure-how-to-fix