When I went through the portal the Ender Dragon left on his death to return to the overworld, the potion effects I had were gone.

Steps to reproduce:
-Go to the end.
-Kill the dragon if it's not dead.
-Get potion effects, either by potions or by the /effect command.
-Check by the inventory key you still have them.
-Pass through the portal the ender dragon left on his death.
-Press the inventory key and you'll see you have no potion effects.