If a point is sampled inside a region where no neighbors are present (or the bubble radius is too small), the localRRT* does not insert it into the tree, for, if the Near-by Vertices set is empty, the algorithm returns without proceeding further with the successive steps of the RRT* (see lines 7-11 of Algorithm 1 in "Anytime Motion Planning using the RRT*")
If a point is sampled inside a region where no neighbors are present (or the bubble radius is too small), the localRRT* does not insert it into the tree, for, if the Near-by Vertices set is empty, the algorithm returns without proceeding further with the successive steps of the RRT* (see lines 7-11 of Algorithm 1 in "Anytime Motion Planning using the RRT*")