Is here a node missing when using the node voltage method?
There is actually no point adding node "n3", because node "n0" and node "n3" are short circuited. If you try to solve it like this, there is actually no problem if you keep in mind that they have the same potential (Vno = Vn3), but there is no reason to make things complicated. Try to avoid extra unknowns :)

Also, there is no element between those two nodes, hard wiring is not considered as an element, so that is not a branch.