fix(jsonapi): handle missing attributes in ErrorNormalizer

[daFish]

Fixes undefined array key warning when normalizing exceptions that don't have attributes in their normalized structure.

This typically occurs with ItemNotFoundException when invalid resource identifiers are provided.

Q	A
Branch?	4.2
Tickets	not applicable
License	MIT
Doc PR	not applicable

Description

Fixes an undefined array key warning in ErrorNormalizer when normalizing exceptions that don't have an attributes key in their normalized structure.

Problem

When ItemNotFoundException or similar exceptions are thrown for invalid resource identifiers, the ErrorNormalizer::normalize() method assumes that $jsonApiObject['data']['attributes'] exists, causing a warning.

Solution

Added defensive checks to handle cases where the attributes key is not present, providing a fallback error structure that conforms to the JSON:API specification.