docs: private static Object nullValueForType(final Class<?> expectedClz)
      {
          if (expectedClz == long.class) {
              return VoltType.NULL_BIGINT;
          }
          else if (expectedClz == int.class) {
              return VoltType.NULL_INTEGER;
          }
          else if (expectedClz == short.class) {
              return VoltType.NULL_SMALLINT;
          }
          else if (expectedClz == byte.class) {
              return VoltType.NULL_TINYINT;
          }
          else if (expectedClz == double.class) {
              return VoltType.NULL_FLOAT;
          }
  
          // all non-primitive types can handle null
          return null;
      }