robust error handling to avoid later crashes

aman/sys/aco/Ant.py

@@ -27,6 +27,9 @@ class Ant:
     # Implements function (5)
     def heuristicInformation(self, current : int):
         _, eta, _ = self.RunwayManager.selectArrivalRunway(self.Nodes[current], self.Configuration.EarliestArrivalTime)
+        if None == eta:
+            return -1.0
+
         inboundDelay = eta - self.Nodes[current].Inbound.InitialArrivalTime
 
         # calculate the fraction with a mix of the unused runway time and the delay of single aircrafts
@@ -54,6 +57,10 @@ class Ant:
                 if False == self.InboundSelected[i]:
                     weights.append(self.heuristicInformation(i) / (pheromoneScale or 1))
 
+        # something was wrong in the runway selection
+        if -1.0 in weights:
+            return None
+
         total = sum(weights)
         cumdist = list(itertools.accumulate(weights)) + [total]
         candidateIndex = bisect.bisect(cumdist, random.random() * total)