I expected to be able to have a world loaded and would be able to play

What actually happened was the game crashed before it could load the game

I tried to start the game as usual, by pressing the play button on the launcher,
I then went on to singleplayer and picked a world to play,
the words loading world and building terrain appeared for about 3 seconds before it crashed and a crash report appeared,
after failing to fix this problem myself I pressed on 'report to Mojang'