Hello ,
After looking over your project I found that you were not cleaning up your old widgets after destroying your player. This left a widget on screen with nothing to reference. This is what was causing the access none errors. What I did to fix this was to add a “Get all Widgets Of Class” node (using the UserWidget base class) and ran that into a ForEachLoop that removed all of the widgets from parent. Once the loop body was complete I created the widget as normal. I have provided an example below. I hope that this information helps.
Make it a great day