sl-textarea may throw error on disconnectedCallback because input element is not found

[schilchSICKAG]

Describe the bug

I recently ran into problems using <sl-textarea /> in a Karma test environment. When using the <sl-textarea /> in Karma tests, the following error is thrown: Uncaught TypeError: Failed to execute 'unobserve' on 'ResizeObserver': parameter 1 is not of type 'Element'. It seems the Element reference this.input is not there anymore when disconnectCallback is run. This may easily be prevented by checking for the existence of this.input in the callback.

We already fixed this in our own fork of shoelace (synergy-design-system/synergy-design-system#437) and would also be willing to provide a PR for this problem.

To Reproduce

This is kind of hard to reproduce. Our test suite has more than two hundred tests for various components. However, in smaller setups using Karma I was not able to reproduce this easily.

Browser / OS

• OS: [e.g. Mac, Windows] MacOS
• Browser: [e.g. Chrome, Firefox, Safari] Chrome (instrumented via Karma)
• Browser version: [e.g. 22] 124.0

[schilchSICKAG]

Closed via #1986