[web-php] PR #742: Only "linked" parameters should have pointer cursor

Pull Request: https://github.com/php/web-php/pull/742 Author: cmb69 If a parameter has no target to scroll to, it should not suggest otherwise by changing the cursor to a pointer. Since the scrolling is done via JS, we should also change the cursor via JS.[1] While we're at it, we also fix the potential JS error where we call the .offset() method on an empty jQuery object. [1] <https://github.com/php/doc-en/issues/2071#issuecomment-1354497367> --- Actually, we should not use JS for this "linking", but rather should output anchors (from PhD) to let the browser do this stuff. But for now, this seems to be a viable solution.