fixed findbugs problem

src/main/java/it/unibz/inf/isochrone/network/NodeConnection.java

@@ -149,7 +149,11 @@ public class NodeConnection {
 	}
 
 	private static Collection<Integer> getRoutesToTargetNode(final Map<Node, Collection<Link>> m, final int nodeId) {
-		final Collection<Link> linkSet = m.get(nodeId);
+		return getRoutesToTargetNode(m, getNodeById(m, nodeId));
+	}
+
+	private static Collection<Integer> getRoutesToTargetNode(final Map<Node, Collection<Link>> m, final Node node) {
+		final Collection<Link> linkSet = m.get(node);
 		final Set<Integer> resultSet = new HashSet<>(linkSet.size());
 		for (final Link l : linkSet) {
 			resultSet.add(l.getRoute());