/* CMD_TERRAFORM_LAND may append further items to _cleared_object_areas,

		 * however it will never erase or re-order existing items.

		 * _cleared_object_areas is a value-type SmallVector, therefore appending items

		 * may result in a backing-store re-allocation, which would invalidate the coa pointer.

		 * The index of the coa pointer into the _cleared_object_areas vector remains valid,

		 * and can be used safely after the CMD_TERRAFORM_LAND operation.

		 * Deliberately clear the coa pointer to avoid leaving dangling pointers which could

		 * inadvertently be dereferenced.

		 */

		assert(coa >= _cleared_object_areas.Begin() && coa < _cleared_object_areas.End());

		size_t coa_index = coa - _cleared_object_areas.Begin();

		coa = NULL;

		_cleared_object_areas[coa_index].first_tile = old_first_tile;