fix: dont attempt pessimistic on NotSerializableException

[mcollovati]

Description

When optimistic serialization fails with NotSerializableException it does not make sense to attemp pessimistic approach, since it will fail with the same error.

Fixes #49

Type of change

• [X] Bugfix
• [ ] Feature

Checklist

• [X] I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• [X] I have added a description following the guideline.
• [X] The issue is created in the corresponding repository and I have referenced it.
• [X] I have added tests to ensure my change is effective and works as intended.
• [X] New and existing tests are passing locally with my change.
• [X] I have performed self-review and corrected misspellings.

Additional for Feature type of change

• [ ] Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.