`getAsync` silent crash

[underflow00]

The simplest use of getAsync causes the program to crash silently when the key doesn't exist

(async () => {
  let rootDb = lmdb.open({
      path: './lmdb-test/db2',
      mapSize: 1024 * 1024 * 1024,
      maxDbs: 10,
      keyEncoding: 'binary',
      encoding: 'binary',
  });
  const value = await rootDb.getAsync(Buffer.from('key1'));
  console.log('done'); // Never executed
})();

Separately, the TypeScript type is also incorrect as it's a single value not an array.

[kriszyp]

getAsync is undocument and unsupported (because it crashes). Use prefetch instead.