Same with non-modded jar 😞 hope u are able to find the problem. thank you anyway for noticing
I got exaclty the same issue. I started playing my world in 1.2.5. I went to the end killed the dragon and never went back again. Now at 1.4.7 i wanted to go back again but it crashes. i can see some end blocks but the game crashes 😞
Deleting DIM1 Folder solves the Problem. You have to Fight the Enderdragon again but anyway i am able to get to the end and get some endstone.