Fix PHP deprecation notice in View Results block

[donnapep]

Proposed Changes

Fixes a deprecation notice in the View Results block:

PHP Deprecated:  parse_str(): Passing null to parameter #1 ($string) of type string is deprecated in /Users/donnapep/Local Sites/senseitheme/app/public/wp-content/plugins/sensei/includes/blocks/class-sensei-block-view-results.php on line 78

Testing Instructions

1. Ensure you're using PHP 8.1+.
2. Complete a course as a student.
3. Visit the Courses page.
4. Ensure the above deprecation notice is not logged.

Pre-Merge Checklist

• PR title and description contain sufficient detail and accurately describe the changes
• Acceptance criteria is met
• Decisions are publicly documented
• Adheres to coding standards (PHP, JavaScript, CSS, HTML)
• All strings are translatable (without concatenation, handles plurals)
• Follows our naming conventions (P6rkRX-4oA-p2)
• Hooks (p6rkRX-1uS-p2) and functions are documented
• New UIs are responsive and use a mobile-first approach
• New UIs match the designs
• Different user privileges (admin, teacher, subscriber) are tested as appropriate
• Legacy courses (course without blocks) are tested
• Code is tested on the minimum supported PHP and WordPress versions
• User interface changes have been tested on the latest versions of Chrome, Firefox and Safari
• "Needs Documentation" label is added if this change requires updates to documentation
• Known issues are created as new GitHub issues

[github-actions]

Test the previous changes of this PR with WordPress Playground.