Ender Dragon fails to spawn with End portal

I have an older minecraft world in which i wanted to load a new end dimension in so i deleted the DIM1 file and when I go to the end the towers are in the circle but no Ender Dragon or portal in the middle

What I expected to happen was...:
End island correctly spawns in with portal in the middle and Ender Dragon ready to kill me

What actually happened was...:
End island spawns correctly with no dragon or portal in the middle

Steps to Reproduce:
1. Have a previous version of a world
2. Have a generated end biome
3. Delete DIM1
4. Go back to portal to enter dimension