EdgeShape:getNextVertex
Gets the vertex that establishes a connection to the next shape.

Setting next and previous EdgeShape vertices can help prevent unwanted collisions when a flat shape slides along the edge and moves over to the new shape.
x, y = EdgeShape:getNextVertex()
x number The x-component of the vertex, or nil if EdgeShape:setNextVertex hasn't been called.
y number The y-component of the vertex, or nil if EdgeShape:setNextVertex hasn't been called.