useResizeObserver doesn't work with changing refs

[Sandro Scheiwiller]

Changing refs, like in the following example, leads to both DOM nodes being observed, since the first node is never unobserved.

const DOMRect = useResizeObserver(first ? ref1 : ref2);

Example: https://codesandbox.io/s/black-dew-36k642?file=/src/App.js

1. First box is being observed, second box not.
2. Click button.
3. Expected: Second box should be observed, first box not. Actual behaviour: Both boxes are observed.

[Rù]

@sandrosc you should use two different useResizeObserver for ref1 and ref2