[crud] Flaky test failing related to trapFocus logic in WebKit

[web-padawan]

What is the problem?

There is a test that often fails in CI only in WebKit:

packages/crud/test/crud-editor.test.js:

 🚧 Browser logs:
      TypeError: undefined is not an object (evaluating 'this.__focusableElements[0].focus')
        at trapFocus (packages/a11y-base/src/focus-trap-controller.js:90:34)
        at _trapFocus (packages/overlay/src/vaadin-overlay-focus-mixin.js:103:45)
        at packages/overlay/src/vaadin-overlay-mixin.js:270:26
        at callMethod (node_modules/@polymer/polymer/lib/utils/render-status.js:[53](https://github.com/vaadin/web-components/actions/runs/14707207961/job/41270716224?pr=9015#step:6:54):19)
        at runQueue (node_modules/@polymer/polymer/lib/utils/render-status.js:44:15)
        at node_modules/@polymer/polymer/lib/utils/render-status.js:31:15

 ❌ crud editor > custom form > should move custom form when editorPosition changes from bottom to default
      Error: TypeError: undefined is not an object (evaluating 'this.__focusableElements[0].focus') (http://localhost:8000/node_modules/@polymer/polymer/lib/utils/render-status.js:[56](https://github.com/vaadin/web-components/actions/runs/14707207961/job/41270716224?pr=9015#step:6:57))
        at node_modules/@web/test-runner-mocha/dist/autorun.js:1:258627