Hello, welcome to the community!
When you are calling the function GetControlledPawn, you are missing to specify a target. You need to provide a Controller if you want to ask that controller for its controlled pawn.
Are you trying to move a character to the player position? Maybe you can use “SimpleMoveToLocation” for that. You just provide the IAController of the character that you want to move and the goal vector.
Also, one recommendation when using EventTick. Are you sure that you need to call that function once per frame? If the answer is no, then EventTick is not the best place to call it (Take a look at timers for that).