Creepers don't cause damage to the environment if standing on a waterlogged top slab

The bug

If a creeper is standing on top of a waterlogged top slab while exploding, it won't cause any damage to its surrounding blocks.

To reproduce

1. Make sure that /gamerule mobGriefing returns true
2. Place a top slab in the ground
3. Waterlog it
4. Spawn a creeper on top of it
5. Ignite it with a flint and steel
   → The creeper won't cause any damage to its surrounding blocks