EnemyPlayer is none at might of calling SetKillStreak, there for funtion fails. You need yo figure why EnemyPlayer is not set in right moment.
Moderator - sorry about the spawn post; my internet was not loading a posted message;
Shadow- I dont understand what enemy player has to do with that widget I am creating. It does not tie into it spawning
Try to debug then put breakpoint on SetKillStrick