[mirror net] Asset amount cannot be negative (reward_balance)

While testing tm-blockchain-converter-new-serialization when mirror chain operation was restored after long break cli_wallet's info command fails with:

10 assert_exception: Assert Exception
vo.amount >= 0: Asset amount cannot be negative
    {}
    asset.cpp:587 from_variant

    {}
    asset.cpp:597 from_variant

because reward_balance is negative:

{
  "jsonrpc": "2.0",
  "result": {
    "id": 0,
    "name": "post",
    "reward_balance": {
      "amount": "-1923756265",
      "precision": 3,
      "nai": "@@000000021"
    },
    "recent_claims": "68052576757220827",
    "last_update": "2021-11-05T07:23:12",
    "content_constant": "2000000000000",
    "percent_curation_rewards": 5000,
    "percent_content_rewards": 10000,
    "author_reward_curve": "linear",
    "curation_reward_curve": "linear"
  },
  "id": 6
}