So I was messing around in creative mode and thought it would be funny to do some weird stuff. 

I tried respawning the ender dragon using End Crystals and typed /kill @e midway through the process. After 2 seconds or so my game crashed (i tried it a couple of times again, it crashes all the time).

When loading up the world sometimes some of the end crystal beams are still there but don't do anything.

How to recreate the bug:

• Go to the end
• Kill ender dragon (however you'd like)
• After the end portal opens up place 4 end crystals on each side to respawn the Dragon 
• Wait until the beams start putting back the end crystals on the obsidian pillars
• Type in /kill @e
• Boom, game crashes

This isn't really such a big deal, but I thought it'd be worth reporting!