Patch

The best easy way is to simulate the directory path, so lets assume you will need to fix the comparison page after you upgrade to Magento 2.3.5-p2

Filename: vendor/magento/module-catalog/Helper/Output.php

we need to replace this line 

- if (preg_match($pattern, $attributeHtml)) {

with this line 

+ if (preg_match($pattern, (string) $attributeHtml)) {

Now create those directories vendor/magento/module-catalog/Helper