WordPress PHP 8.3 Compatibility Fix – Custom Theme Debugging

I require an experienced WordPress PHP developer to resolve a PHP 8.3 fatal error caused by a custom legacy theme (built in 2014).

The Issue:
- Clicking "Add New Page" (wp-admin/post-new.php) triggers a WordPress Critical Error screen.
- Server error logs show that legacy theme files attempt to read properties on null objects and undefined variables, which modern PHP 8.3 treats as fatal errors.

Scope of Work:
- Audit and patch the custom theme code in /wp-content/themes/heatherhall2014/ to ensure full PHP 8.3 compatibility.
- Ensure the Block Editor opens cleanly without breaking existing shortcode functions on published pages.

Requirements:
- Strong background in WordPress core development, PHP 8.x syntax, and theme debugging.
- Ability to complete the fix safely via cPanel / File Manager (credentials provided in private chat once hired).
- Fixed-price quote preferred.