Logging null building

src/engine/objects/Mob.java

@@ -1557,11 +1557,15 @@ public class Mob extends AbstractIntelligenceAgent implements Delayed {
             case GuardCaptain:
                 this.agentType = AIAgentType.GUARDCAPTAIN;
                 this.spawnDelay = 600;
+                if (this.building == null)
+                    Logger.error("Captain : " + this.getObjectUUID() + " : " + this.buildingUUID);
                 this.guardedCity = ZoneManager.getCityAtLocation(this.building.getLoc());
                 break;
             case GuardWallArcher:
                 this.agentType = AIAgentType.GUARDWALLARCHER;
                 this.spawnDelay = 450;
+                if (this.building == null)
+                    Logger.error("Wall Archer : " + this.getObjectUUID() + " : " + this.buildingUUID);
                 this.guardedCity = ZoneManager.getCityAtLocation(this.building.getLoc());
                 break;
         }