Turn if/else branch for valid compare error message
Created by: Razer6
What does this MR do?
This PR switches the error messages, if compare logic can't provide a comparison result.
Why was this MR needed?
If we're comparing the same revision, UI says You'll need to use different branch names to get a valid comparison.. If it can't compare for some reason (e.g. branch doesn't exist), it says branch1 and master are the same.
What are the relevant issue numbers?
This is related to #7446 (closed)