In a creative world in the 1.16 pre-release, the first time I enter a Nether portal in a world, it works perfectly, but once I leave the Nether, and try to re-enter, it crashes and gives me the error: 

The game crashed while ticking player

Error: java.lang.NullPointerException: Ticking player

I tried re-entering the world and entering the Nether, but the same error occurs every time. I have attached the crash report and a screenshot of the launcher message.