Selection of the description does not work in Firefox

[QuickWrite]

Describe the bug
The selection of the description of the code does not work as intendet as the selection wraps around the codeblock.

To Reproduce
Steps to reproduce the behavior:

1. Create a <multicodeblock> that has multiple description blocks.
2. Use Firefox
3. Select a region with the mouse on the description side.
4. Select under the description block
5. The code should be highlighted

Expected behavior
The codeblock shouldn't be highlighted and shouldn't be able to be copied.

Screenshots

Desktop (please complete the following information):

• OS: Windows
• Browser Firefox
• Version 90.0.0.2 (64 Bit)

Additional context
This is just an error with Firefox/ Gecko and does not apply on Chrome (Blink)