https://answers.unrealengine.com/questions/263231/error-accessed-none-1.html
EDIT: - YouTube a quick video
Nobody is answering so I decided to take the matter here 
There is also something I found. When I make a reference variable and make it public. I add BP_Character to the viewport and try to edit the Equipped Weapon, but in the dropdown there are no blueprints to select. Also when I try to drag blueprint over it, it gets red dashed border.
The pointer variable “Equipted Weapon” is null when using it. That is forbidden! Use an “IsValid” node for all your pointers before actually using them.
This is basic C (not even C++). If you don’t understand what i’m talking about, watch this video of me:
PS: The drop down is empty, because you can only fill Spawned Actors there. If you have no weapon spawned, you won’t find anything to fill it with.
Ok I understand now, but in the BP_Character I have set EquippedWeapon to be a reference to BP_Weapon_AK74.
Doesn’t that mean it’s not null and is valid, because when I try to verify with IsValid it returns it is not valid 
I can put my entire project in .rar and send it to you to check