Strange error/warning in uncertain model with linear equality

[johanlofberg]

yalmip('clear')
Pg_un=sdpvar(3,1,'full');
W=[0<=Pg_un(1)<=2,uncertain(Pg_un(1))];
Cons=[Pg_un(1)+Pg_un(2)==5,...
      Pg_un(2)-Pg_un(3)<=2];
fmin=Pg_un(3);
optimize(Cons+W, fmin);