City check moved outside of validation

src/engine/gameManager/ForgeManager.java

@@ -105,7 +105,13 @@ public enum ForgeManager implements Runnable {
         if (validation_result != 0)
             return validation_result;
 
+        // Concurrency is managed by same lock as warehouse
+
         City city = workOrder.vendor.building.getCity();
+
+        if (city == null)
+            return 58; //58: The formula is beyond the means of this facility
+
         city.transactionLock.writeLock().lock();
 
         try {