Fix blank screen is displayed during OBW when using WP5.9

[chihsuan]

All Submissions:

• Have you followed the WooCommerce Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Closes #36711.

When a site downgrades WP to a lower version with an incompatible active theme, it leads to a fatal error when clicking "Continue" on "Business Details" step because theme data is incomplete.

This PR adds a check to exclude the active theme from onboarding themes if it's incompatible.

• This PR is a very minor change/addition and does not require testing instructions (if checked you can ignore/remove the next section).

How to test the changes in this Pull Request:

• Have you followed the Writing high-quality testing instructions guide?

1. Create a test site using Jurassic Ninja (ensure to check the box for WP Downgrade) or use a WP 6.1 site with Twenty Twenty-Three theme active.
2. Downgrade the version of WP to 5.9 PbPjnJ-1eN-p2
3. Start with OBW.
4. Go to Business Details > Free feature step.
5. Click Continue.
6. Observe that Blank Screen is NOT displayed, but a theme screen is shown.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you created a changelog file for each project being changed, ie pnpm --filter=<project> changelog add?

FOR PR REVIEWER ONLY:

• I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.

[github-actions]

Test Results Summary

Commit SHA: d5163f9

Test 🧪	Passed ✅	Failed 🚨	Broken 🚧	Skipped ⏭️	Unknown ❔	Total 📊	Duration ⏱️
API Tests	259	0	0	2	0	261	1m 3s
E2E Tests	189	0	0	6	0	195	13m 30s

---

To view the full API test report, click here.
To view the full E2E test report, click here.
To view all test reports, visit the WooCommerce Test Reports Dashboard.

[codecov]

Codecov Report

Merging #36903 (3d7b765) into trunk (2e146d5) will decrease coverage by 0.0%.
The diff coverage is n/a.

❗ Current head 3d7b765 differs from pull request most recent head d5163f9. Consider uploading reports for the commit d5163f9 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             trunk   #36903     +/-   ##
==========================================
- Coverage     46.7%    46.7%   -0.0%     
+ Complexity   17171    17168      -3     
==========================================
  Files          429      429             
  Lines        64762    64748     -14     
==========================================
- Hits         30220    30207     -13     
+ Misses       34542    34541      -1     

Impacted Files	Coverage Δ
plugins/woocommerce/includes/wc-core-functions.php	54.9% <0.0%> (-0.2%)	⬇️
plugins/woocommerce/includes/class-wc-tracker.php	89.7% <0.0%> (-<0.1%)	⬇️

[rjchow]

Works as expected! Thanks for fixing this!

[ilyasfoo]

Apologies for the delayed review. Tested well, thanks! 🚢