Convert from Uint8Array to Buffer

No, you have to actually call `.toJSON()`.  Should be:

```js
  // We do extra work to make sure typed buffer survive
  // being stored on disk and still get the right prototype later.
  if (Buffer.isBuffer(value)) {
    var data = value.toJSON();
    value = {
      __isBuffer: true,
      // Deal with difference between versions of node and .toJSON()
      __data: data.data || data
    };
```