Fix display shortcode php buffer

[randhirexpresstech]

Issue: Output buffer not being flushed in case of invalid quiz id
https://app.clickup.com/t/86cv6dj67
Steps to reproduce

1. Install and activate breakdance plugin
2. Go to breakdance > settings > theme > Disable Theme > save
3. Install and activate Quiz And Survey Master plugin
4. Create header in breakdance.
5. Add a invalid QSM quiz shortcode in a page created by breakdance and publish the page
6. Visit the publish page

Merge Checklist

Please check all of the following items before merging

• No new WPCS issues
• No notices, warnings or errors in debug.log
• No sonar cloud issues
• No errors while running automated tests

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud