message: Use std::map::at instead of operator[] in ProductPool
diff: @@ -32,7 +32,7 @@ std::map<ProductType, int> PRODUCT_STORAGE_VALUE =
  */
  inline int storageRequiredPerUnit(ProductType type)
  {
  - return PRODUCT_STORAGE_VALUE[type];
  + return PRODUCT_STORAGE_VALUE.at(type);
  }
  @@ -41,7 +41,7 @@ inline int storageRequiredPerUnit(ProductType type)
  */
  int storageRequired(ProductType type, int count)
  {
  - return PRODUCT_STORAGE_VALUE[type] * count;
  + return PRODUCT_STORAGE_VALUE.at(type) * count;
  }
  