Steps to reproduce:

1. Create new content type and add a Text Line field to it.
2. Create ger-DE language.
3. Create and publish content of this content type and translate it to English.
4. Edit content type from step 1. and add a non-translatable checkbox field to it.
5. Edit content from step 3., select checkbox and publish it.

Result:
One is presented with an exception.

Undefined array key

or

Ibexa\Core\Persistence\Legacy\Content\FieldHandler::updateCopiedField(): Argument #3 ($originalField) must be of type Ibexa\Contracts\Core\Persistence\Content\Field, null given, called in /app/vendor/ibexa/core/src/lib/Persistence/Legacy/Content/FieldHandler.php on line 369 [in vendor/ibexa/core/src/lib/Persistence/Legacy/Content/FieldHandler.php:393]

Expected result:
Content should be published without an exception.