ItEr57S04ValidacionEProbasFuncionaisItEr56S04: Fix bug.

When a limiting tasks has no outgoing dependencies an empty graph was
produced and this caused an assertion at TopologicalOrderIterator to
fail.

navalplanner-webapp/src/main/java/org/navalplanner/web/limitingresources/QueuesState.java

@@ -316,6 +316,7 @@ public class QueuesState {
             LimitingResourceQueueElement element) {
         Set<LimitingResourceQueueDependency> outgoingEdgesOf = graph
                 .outgoingEdgesOf(element);
+        result.addVertex(element);
         for (LimitingResourceQueueDependency each : outgoingEdgesOf) {
             addDependency(result, each);
             buildOutgoingGraphFor(result, each.getHasAsDestiny());