Put the summary of the bug you're having here

What I expected to happen was...:
I thought the Ender Dragon Egg appearing next to an observer block would trigger it.

What actually happened was...:
When the Ender Dragon Egg appeared next to the observer block, it did not trigger it.

Steps to Reproduce:
1. Either place a bunch of observer blocks with pistons next to them and keep clicking on dragon eggs until one lands next to an observer block, or...
2. Fill up the radius of a dragon egg's teleportation with blocks and leave one block free so that the egg must teleport there. Make that free block next to an observer block.