strpos() and htmlspecialchars() related warning messages on help page

I verified the bug. The help page at /admin/help/styleguide crashes with an error about a Url object being passed instead of a string. The solution in the MR fixes the page and there are no more errors showing up in the site log. It's a simple bug with an easy fix. This is RTBC.

Thanks for the MR, @david.czinege!

dcam → changed the visibility of the branch 3248027-fix-help-page to hidden.

Automatically closed - issue fixed for 2 weeks with no activity.