copy paste mysteries with ghost nodes and disappearing connections

src/main.cpp

@@ -295,7 +295,7 @@ int main(){
 			}
 			case InteractionState::PASTE_SELECTED_NODES:
 			{
-				for(auto &n: copied_nodes){
+				for(auto n: copied_nodes){
 					n->drag_offset = (n->position - copied_nodes.front()->position);
 				}
 				app.copyNodesAndConnections(copied_nodes, mouse_pos);