Fix Bug setting active hover to undefined

Hi! 👋

Firstly, thanks for your work on this project! 🙂

Today I used [patch-package](https://github.com/ds300/patch-package) to patch `chart.js@4.4.8` for the project I'm working on.

Here is the diff that solved my problem:

```diff
diff --git a/node_modules/chart.js/dist/chart.js b/node_modules/chart.js/dist/chart.js
index e67f0ee..6021286 100644
--- a/node_modules/chart.js/dist/chart.js
+++ b/node_modules/chart.js/dist/chart.js
@@ -1029,6 +1029,7 @@ class DatasetController {
}
}
_setStyle(element, index, mode, active) {
+ if (!element) return;
element.active = active;
const options = this.getStyle(index, active);
this._resolveAnimations(index, mode, active).update(element, {
```

This issue body was [partially generated by patch-package](https://github.com/ds300/patch-package/issues/296).