I have read many of the replies to this problem, but if you simply want to fix this problem quickly and continue to use your vintage MacBook Pro without all the tweaking, do this. Install Amphetamine (free), set it to “Indefinitely” for the session, and check “Allow display sleep”. While this may not seem like the optimal solution, it works and kernel panic is no more! Just keep your machine plugged in when not in use. A bonus is that it will run faster too! (see screenshot).
