Unresolved external symbol when casting to AAIController

AIController.h

OK I give up. It works so my confusion is irrelevant. Cheers and see you around!

OMG, I wasted 3 hours on this! I am relatively new to C++ (coming from 15 years C# dev experience).

Why in the hell is this not documented anywhere? Really contemplating going to Unity as the DEV non-BP experience so far is appalling!