Resolve "Improve JUnit support"

What does this MR do?

• fix an array check that was missing .length
• reset error state in success response for the cases we go from error to success response. When the page has a push event it will start polling again

How to test locally

Steps to test locally: https://gitlab.com/snippets/1731728#note_92840235

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conforms to the merge request performance guidelines
• Conforms to the style guides

What are the relevant issue numbers?

#49966 (closed)