Without finding the specific issue and attempting to just apply that code specifically, I don't believe there is a simple fix. You could contact Kentico support and find out if they have a simple hotfix application for it. A better method is to not code yourself/client into a corner with non-best practice customizations so you at least have an upgrade path in the future.
Upgrading to v8.2 is not a hard step BUT check out the release notes to see what kind of impact it might have on your project before upgrading.
For your actual problem, you could hard code the static part of the url URL and create your own macro to get the hash value that is created for that user to finish the URL off.