Thank you for replying night watcher!! I hadn’t put anything into the construction scripts, but you helped me look harder and find the root issue! For anyone having a similar problem later down the line, what caused the accessed none in my case was that I had my BP character dropped into the level, and my game mode was set to spawn my BP character by default (you can change this by clicking game mode, and checking the world settings panel on the right of the editor). For me just switched the game mode player to none, as I like to see my character whether the game is on or not.
But anyways, the game mode’s player that spawned was a duplicate character, but it did not select the spline actor setting in the editor panel - hence the accessed none error.
Thanks for your time Night Watcher, everything is working as expected now!
Hope this might help another noob like me out there later :).