2DSideScroller, execution path doesn't end with a return node. cast failed

trying to give my character some health but its not working! so i just started playing around with unreal engine about 4 days ago and iv been watching this video on how to make a 2d game. iv followed closely but once i get up to the health widget and i try to compile i get an error that says “execution path doesn’t end with a return node. cast failed” Im not an expert on this at all so can someone explain what is going on and how i fix it. i uploaded a screenshot so you can see what ive got going on. also i do believe the video i am watch is using a slightly older version of this engine.