fix: don't show inline JSON editor error for empty value

[AlekseyManetov]

Proposed Changes

Small follow-up tweak for PR #485 to prevent inline editor errors from being shown for empty values.

Before:

After:

Checklist

Ensure you provide everything we need to review your contribution:

• Contribution meets our definition of done
• Pull request establishes context
  • Link to related issue(s), i.e. Closes {LINK_TO_ISSUE} or Related to {LINK_TO_ISSUE}
  • Brief textual description of the changes
  • Screenshots or short videos showing UI/UX changes
  • Steps to try out, i.e. using the @bpmn-io/sr tool

[Copilot]

Pull request overview

Follow-up fix to prevent CodeMirror’s inline JSON lint errors from showing when the JsonEditor value is empty.

Changes:

• Skip JSON parsing linter when the editor content is empty/whitespace-only.
• Add a regression test ensuring no entry error and no inline lint markers for an empty value.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/components/entries/JsonEditor.js	Updates CodeMirror linter behavior to return no diagnostics for empty content.
test/spec/components/JsonEditor.spec.js	Adds validation test case for empty value with no errors shown.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[nikku]

@AlekseyManetov Looks good - please validate if 🤖 assertions for tests hold. We want to ensure that tests are green with the fix, and red (failing) without 🙃

[AlekseyManetov]

@AlekseyManetov Looks good - please validate if 🤖 assertions for tests hold. We want to ensure that tests are green with the fix, and red (failing) without 🙃

@nikku Copilot is wrong on this point. This was my first try with waitFor, but then I realized that it can’t be used for this case, because waitFor polls until the callback passes without throwing. For negative assertions like expect(X).to.not.exist, it succeeds on the very first poll immediately, because the element hasn't appeared yet.

I've run the tests without my fix and they failed, so we're safe here.