TYPO3 Core

Hi,
since switching to PHP8 my logs are flooded with "Undefined array key" warnings.

At one place I render text (creator name) into an image, and to have the text visible against every background color, I give it an outline:

Simplified:

20 = IMG_RESOURCE
20{
   file = GIFBUILDER
   file{
        10 = IMAGE
        10{
           ...
        }
        20 = TEXT
    20 {
      text.data = register:creator
          text.wrap = ©|
          test.required = register:creator 
          # bottom right corner
          offset = [10.w]-3,[10.h]-3
          angle = 90
          fontColor = #FFFFFF
      outline {
        thickness = 1
        if.isTrue.field=rendercreator
        color = #32475b
        color.if.isTrue.field=rendercreator
      }
    }
   }
}

Every line within the outline-block triggers the following Warning (for what ever comes first):

Exception: PHP Warning: Undefined array key "thickness" in /var/www/html/typo3_src-12.4.18/typo3/sysext/frontend/Classes/Imaging/GifBuilder.php line 455

And if I lookup the code in GifBuilder.php it's relatively clear why this warning is triggered:

451  if (is_array($conf['outline.'] ?? null)) {
452      $isStdWrapped = [];
453      foreach ($conf['outline.'] as $key => $value) {
454          $parameter = rtrim($key, '.');
455          if (!$isStdWrapped[$parameter] && isset($conf[$parameter . '.'])) {
456              $conf['outline.'][$parameter] = $this->cObj->stdWrapValue($parameter, $conf);
457              $isStdWrapped[$parameter] = 1;
458          }
459      }
460      $this->makeOutline($this->im, $conf['outline.'], $this->workArea, $conf);
461  }

in line 452 the Array is created empty and in 455 the key "thickness" (for example) is used without it being initialized.

I'm unsure what the best way would be in this case. I think it would suffice to change it to:

455          if (!($isStdWrapped[$parameter] ?? false) && isset($conf[$parameter . '.'])) {

Of course this same change has to be done for all 3 occurrences - I attached a patch file for TYPO3 v12.4.19 but the problem is present in v11 as well

On a side note: this warning at first seemed to be much more catastrophic, because in the settings the value for exceptionalErrors was switched from 4096 (default) to

[SYS][exceptionalErrors] = 12290

This is the second time, this exact change happened - seeing this happen again and "right in front of my eyes" make me think it's the Upgrade Wizard that changes ist - but not always. I'm confused. if any one knows, why this happens please give me a clue.