spaceCatcher causes null-access

[subITCSS]

Describe the bug

We get the following error tracked via Sentry:
can't access property "getAttribute", this.shadowRoot.activeElement is null

which is caused by that code:

_spaceCatcher: function (e) {
    e.preventDefault();
    if (this.shadowRoot != null) {
      var nextPos = this.shadowRoot.activeElement.getAttribute('aria-posinset');
    } else {
      var nextPos = document.activeElement.getAttribute('aria-posinset');
    }
    if (!nextPos)
      return;
    this.movePos(nextPos);
  },

Expected behavior

The code should be able to handle such state.

_spaceCatcher: function (e) {
    e.preventDefault();

    const root = this.shadowRoot || document;
    const activeEl = root.activeElement;

    if (!activeEl) return;

    const nextPosAttr = activeEl.getAttribute('aria-posinset');
    if (!nextPosAttr) return;

    const nextPos = parseInt(nextPosAttr, 10);
    if (Number.isNaN(nextPos)) return;

    this.movePos(nextPos - 1);
  },

Minimal reproducible example

No response

Add-on Version

3.0.1

Vaadin Version

24.10.1

Additional information

No response

[javier-godoy]

Minimal reproducible example

1. Go to https://addonsv25.flowingcode.com/carousel/slide-listener
2. Focus the carousel
3. Press space