getTxBalance returns undefined key balance when accounting creation token transaction proposal

[alexruzenhack]

During the tests for the multisig extension of wallet-headless project, I found that the balance key for a token creation of a transaction proposal is undefined as you can see bellow:

// decode response for a token creation transaction proposal
{
  success: true,
  balance: {
    '00': {
      tokens: { available: -1, locked: 0 },
      authorities: {
        melt: { available: 0, locked: 0 },
        mint: { available: 0, locked: 0 },
      },
    },
    undefined: { // token here is undefined because it is not already created
      tokens: { available: 100, locked: 0 },
      authorities: {
        melt: { available: 1, locked: 0 },
        mint: { available: 1, locked: 0 },
      },
    },
  },
  tx: {...},
}

See:
https://github.com/HathorNetwork/hathor-wallet-headless/blob/fd88de218d00d2f5f86d1873fc3b5d18840e4d76/__tests__/integration/multisig.test.js#L506C12-L506C12

Despite it be correct, undefined conveys the lack of intension, therefore it could be something like this:

'new-token:<token-name>': {
  tokens: { available: 100, locked: 0 },
  authorities: {
    melt: { available: 1, locked: 0 },
    mint: { available: 1, locked: 0 },
  },
},

Related to: HathorNetwork/hathor-wallet-headless#317

[alexruzenhack]

Notify: @r4mmer