-Prevent crashing the sim when starting at a gate that is not connected to the ground network. For now, just silently shut down the ATC system.

src/AIModel/AIFlightPlanCreatePushBack.cxx

@@ -148,9 +148,12 @@ bool FGAIFlightPlan::createPushBack(FGAIAircraft *ac,
 	  FGTaxiNode *tn = dep->getDynamics()->getGroundNetwork()->findNode(gateId);
 	  FGTaxiSegmentVectorIterator ts = tn->getBeginRoute();
 	  FGTaxiSegmentVectorIterator te = tn->getEndRoute();
+	  // if the starting node equals the ending node, then there aren't any routes for this parking.
+          // in cases like these we should flag the gate as being inoperative and return false
 	  if (ts == te) {
 	      SG_LOG(SG_GENERAL, SG_ALERT, "Gate " << gateId << "doesn't seem to have routes associated with it.");
-               //exit(1);
+              parking->setAvailable(false);
+              return false;
 	  }
 	  tn = (*ts)->getEnd();
 	  lastNodeVisited = tn->getIndex();

src/ATC/atc_mgr.cxx

@@ -37,6 +37,7 @@ FGATCManager::FGATCManager() {
     controller = 0;
     prevController = 0;
     networkVisible = false;
+    initSucceeded  = false;
 }
 
 FGATCManager::~FGATCManager() {
@@ -136,7 +137,7 @@ void FGATCManager::init() {
             string aircraftType; // Unused.
             string airline;      // Currently used for gate selection, but a fallback mechanism will apply when not specified.
             fp->setGate(park_index);
-            fp->createPushBack(&ai_ac,
+            if (!(fp->createPushBack(&ai_ac,
                                false, 
                                apt, 
                                latitude,
@@ -144,7 +145,10 @@ void FGATCManager::init() {
                                aircraftRadius,
                                fltType,
                                aircraftType,
-                               airline);
+                               airline))) {
+                controller = 0;
+                return;
+            }
 
         }
         fp->getLastWaypoint()->setName( fp->getLastWaypoint()->getName() + string("legend")); 
@@ -170,6 +174,7 @@ void FGATCManager::init() {
    //cerr << "Adding groundnetWork to the scenegraph::init" << endl;
    //globals->get_scenery()->get_scene_graph()->addChild(node);
    }
+   initSucceeded = true;
 }
 
 void FGATCManager::addController(FGATCController *controller) {

src/ATC/atc_mgr.hxx

@@ -52,6 +52,7 @@ private:
   FGATCController *controller, *prevController; // The ATC controller that is responsible for the user's aircraft. 
   //FGATCDialogNew dialog;  // note that this variable should really replace the ugly global "currentATCDialog();
   bool networkVisible;
+  bool initSucceeded;
 
 public:
   FGATCManager();