[TASK] Avoid console error in hotkey module

Cope with the situation that a KeyboardEvent is not guaranteed
to provide a `key` property in the event struct. `key` will
be undefined if a input value is filled from a autocomplete list
in google chrome.

Releases: main
Resolves: #104389
Change-Id: I7e3d557a1026398c44b3511ec5495bfd188d19b5
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85257


Tested-by: core-ci <typo3@b13.com>
Tested-by: Guido Schmechel <guido.schmechel@brandung.de>
Reviewed-by: Guido Schmechel <guido.schmechel@brandung.de>
Reviewed-by: Garvin Hicking <gh@faktor-e.de>
Reviewed-by: Benjamin Franzke <ben@bnf.dev>
Tested-by: Garvin Hicking <gh@faktor-e.de>
Tested-by: Benjamin Franzke <ben@bnf.dev>