RM-343: Fix Create KB article page crashing on reload

[biast12]

RM-343

Description

Fixes a crash when reloading the Create KB article page: TypeError: Cannot read properties of undefined (reading 'getMarkdown').

On a hard reload, React holds back showing the lazy-loaded page (up to 300 ms after the loading fallback). Tiptap's useEditor destroys the editor it created during render if the component hasn't mounted within 1 ms, and destroy() clears editor.storage. MarkdownEditor's value-sync effect then read storage.markdown on that destroyed editor and threw.

Type of Change

• Bug fix
• New feature
• Breaking change

Testing

• Try to create a KB
• Reload the create page

Checklist

• My code follows the style of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works