"Accessed None trying to read property"

[99bullets]

Hey ! i have a small problem, i don't understand why i made a menu UI that worked nice since now, i have a backup of my menu and it works well, i changed nothing and it tell me ""Accessed None trying to read property UI"

i show you my BP :

https://answers.unrealengine.com/sto...3323-dedes.png

here is my "Main UI"

https://answers.unrealengine.com/sto...3324-szssz.png

https://answers.unrealengine.com/sto...3325-dedez.png

Thanks !