[Bug] SP Page Builder Pro 6.9 Contact Form fails with Joomla Proof of Work CAPTCHA

Environment:

• Joomla 6.1.3 Stable
• SP Page Builder Pro 6.9.1
• Helix Ultimate
• Contact Form addon
• Joomla built-in Proof of Work CAPTCHA enabled

Problem:

The SP Page Builder Contact Form does not submit when Joomla's Proof of Work CAPTCHA is enabled.
Instead of the AJAX request, the browser performs a normal GET request to index.php and reloads the page.

The browser console shows:

Uncaught TypeError: can't access property "includes", t(...).attr(...) is undefined
    sppagebuilder.js:1779

The failing code is:
if (t(this).attr('name').includes('sppb-hpt_')) return !0;

The element causing the error is the checkbox generated by the Proof of Work CAPTCHA. It has no "name" attribute, for example:
<input id="custom_captcha_..." type="checkbox" required>

Therefore t(this).attr('name') returns undefined and .includes() throws an exception.

It looks like the form validation code assumes that every input element has a name attribute, which is not true for the checkbox generated by Joomla's Proof of Work CAPTCHA.

Reproduction:

1. Create an SP Page Builder Contact Form.
2. Select and Enable Joomla's Proof of Work CAPTCHA.
3. Open the page.
4. The JavaScript exception occurs during page initialization.
5. Submit the contact form.
6. The AJAX submit handler is not active due to the initalization failure, so the form falls back to a normal GET request to index.php.

Control test:

• Disable Proof of Work CAPTCHA.
• The contact form works correctly.
• AJAX response is successful.
• Recipient receives the email.

Temporary fix:

Changing the line which throws the exception from:

if (t(this).attr('name').includes('sppb-hpt_')) return !0;

to:

if ((t(this).attr('name') || '').includes('sppb-hpt_')) return !0;

fixes the issue.

After this change:

• Proof of Work CAPTCHA remains enabled
• AJAX submission works
• recipient receives the email
• copy to applicant works