fixes for proper zone cleanup

see #144

server/src/board/tile/rail/blockrailtile.cpp

@@ -33,6 +33,7 @@
 #include "../../../train/traintracking.hpp"
 #include "../../../utils/displayname.hpp"
 #include "../../../zone/blockzonelist.hpp"
+#include "../../../zone/zoneblocklist.hpp"
 #include "../../list/blockrailtilelist.hpp"
 #include "../../list/blockrailtilelisttablemodel.hpp"
 #include "../../map/blockpath.hpp"
@@ -569,6 +570,10 @@ void BlockRailTile::destroying()
   {
     trains.back()->destroy();
   }
+  for(const auto& zone : *zones)
+  {
+    zone->blocks->remove(self);
+  }
   m_world.blockRailTiles->removeObject(self);
   RailTile::destroying();
 }

server/src/zone/zone.cpp

@@ -24,6 +24,7 @@
 #include "zoneblocklist.hpp"
 #include "zonelist.hpp"
 #include "zonelisttablemodel.hpp"
+#include "blockzonelist.hpp"
 #include "../core/attributes.hpp"
 #include "../core/objectproperty.tpp"
 #include "../core/objectvectorproperty.tpp"
@@ -126,6 +127,17 @@ void Zone::addToWorld()
   m_world.zones->addObject(shared_ptr<Zone>());
 }
 
+void Zone::destroying()
+{
+  auto self = shared_ptr<Zone>();
+  for(const auto& block : *blocks)
+  {
+    block->zones->remove(self);
+  }
+  m_world.zones->removeObject(self);
+  IdObject::destroying();
+}
+
 void Zone::fireTrainAssigned(const std::shared_ptr<Train>& train)
 {
   fireEvent(onTrainAssigned, train, shared_ptr<Zone>());

server/src/zone/zone.hpp

@@ -44,6 +44,7 @@ class Zone : public IdObject
 protected:
   void worldEvent(WorldState worldState, WorldEvent worldEvent) override;
   void addToWorld() override;
+  void destroying() override;
 
   void fireTrainAssigned(const std::shared_ptr<Train>& train);
   void fireTrainEntering(const std::shared_ptr<Train>& train);