fix: serialize item of type array with zero

[chrysomallos]

Currently the serialize in dynamodb will return [null, null] instead of [0, 0].
Issue found in a not correct check at lib/serializer.js:142, the values 0 and '' are result as null, because they are truish at this check.
Result of new test case without the changes on lib/serializer.js to see the issue:

Serializer
       #serializeItem
         should serialize number array with zeros:

      AssertionError: expected { id: 1, resolution: [ null, null ] } to deeply equal { id: 1, resolution: [ +0, +0 ] }
      + expected - actual

       {
         "id": 1
         "resolution": [
      -    [null]
      -    [null]
      +    0
      +    0
         ]
       }

      at Context.<anonymous> (test\serializer-test.js:543:19)
      at process.processImmediate (node:internal/timers:476:21)