TYPO3 Core

Hello, I have an issue with typo3 v11.5.15, php8.1: PHP Warning: Undefined array key "userFunc."
The issue comes from the file: typo3/sysext/core/Classes/Html/HtmlParser.php L580 (screenshot of the code)
Has you can see on the line 580 typo3 doesn't check if the array key "userFunc." exists, whereas on the top of this line, the check of the existence of the array key "userFunc" is done.
We though it might be a bad configuration from our side but then, why the 'else' acts like if the previous 'if' doesn't work, do something totally different?