Method made static and moved to manager.

src/engine/workthreads/DestroyCityThread.java

@@ -19,6 +19,7 @@ package engine.workthreads;
  */
 
 import engine.Enum;
+import engine.gameManager.BuildingManager;
 import engine.gameManager.DbManager;
 import engine.gameManager.GuildManager;
 import engine.gameManager.ZoneManager;
@@ -127,7 +128,7 @@ public class DestroyCityThread implements Runnable {
                     || (cityBuilding.getBlueprint().getBuildingGroup() == Enum.BuildingGroup.WAREHOUSE)) {
 
                 if (cityBuilding.getRank() != -1)
-                    cityBuilding.setRank(-1);
+                    BuildingManager.setRank(cityBuilding, -1);
             }
         }