Hotfix 2.0.x SUP-16159 Improve WebSocket error handling

[yrucrem]

Abstract

Errors from Vert.x when creating an eventbus WebSocket where not handled which caused a NullPointerException during event creation. Typical errors like invalid event addresses are now handled, and multiple registrations of the same address no longer lead to errors.

Checklist

General

• [ ] Added abstract that describes the change
• [ ] Added changelog entry to /CHANGELOG.adoc
• [ ] Ensured that the change is covered by tests
• [ ] Ensured that the change is documented in the docs

On API Changes

• [ ] Checked if the changes are breaking or not
• [ ] Added GraphQL API if applicable
• [ ] Added Elasticsearch mapping if applicable

[yrucrem]

Will be upmerged from hotfix-1.10.x.