Zombie Reinforcements can spawn on glass

The bug

In my singleplayer survival world I built Ilmango's Gold Farm, and for some reason since I updated to 1.14.2 zombies can spawn on the glass floor surrounding my AFK spot and kill me. I googled the problem and I'm not the only one who has had it. There was this post on the minecraft forum:

https://www.minecraftforum.net/forums/minecraft-java-edition/recent-updates-and-snapshots/2961022-do-zombie-reinforcements-spawn-on-glass-glass-now

To reproduce

1. Create a new void world
2. Replace the stone platform completely with glass
3. Set difficulty to hard
4. Set time to night
5. Spawn a bunch of zombies
6. Punch them
   → Zombie reinforcements spawn