When equipped with the Elytra, if you activate Elytra flight and hold space while in creative mode, you will shoot up into the sky. Upon flying back down to the ground, all of the terrain will be invisible, and the only way I've fixed the terrain is by restarting the game (i didn't try other possible ways of fixing it). You can still generate new terrain, but the terrain that disappeared doesn't come back.

I have reproduced it multiple times :

1 ) Equip an Elytra in creative mode

2 ) Activate Elytra flight

3 ) Press and hold space until you can no longer see the terrain below you.

4 ) Upon returning to the ground, every block is invisible.

I recorded the bug aswell. 

https://streamable.com/77r38g