[#1516] traverser: Check for placement vector out of range

Placement vector may contain fewer nodes count than it required by policy
due to the outage of the one of the node.

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

pkg/services/object_manager/placement/traverser.go

@@ -114,8 +114,9 @@ func NewTraverser(opts ...Option) (*Traverser, error) {
 		var unsortedVector []netmap.NodeInfo
 		var regularVector []netmap.NodeInfo
 		for i := range rem {
-			unsortedVector = append(unsortedVector, ns[i][:rem[i]]...)
-			regularVector = append(regularVector, ns[i][rem[i]:]...)
+			pivot := min(len(ns[i]), rem[i])
+			unsortedVector = append(unsortedVector, ns[i][:pivot]...)
+			regularVector = append(regularVector, ns[i][pivot:]...)
 		}
 		rem = []int{-1, -1}