End Crystal Duplication Glitch in Minecraft 1.10.2

I was playing Minecraft 1.10.2 and wanted to respawn the Ender Dragon.
I placed my crystals on the portal, but Nothing happened, since I have beaten the dragon in my world before 1.9.
I exited the world and joined back in, to find my End Crystals back in my inventory, as well as seeing them placed on the portal. The crystals on the portal were fully functionning (explode on contact with a hit) and the ones in my inventory could be placed as well as explode.

Steps to reproduce:
-Have End Crystals
-Place down in the End (I haven't tried in the overworld)
-Save and Quit
-Join the same world again.