To help people with a solution put a DelayUntilNextTick node (or just a regular delay in UE4). If you wait a frame it will be valid on the next frame. Unfortunately neither Construct or Initialized means that its a valid reference yet.
The “real” error:
LogPlayerController: Error: InputMode:UIOnly - Attempting to focus Non-Focusable widget SObjectWidget [Widget.cpp(954)]!
