Problem: TxDecoder fails to decode transaction with legacy multisig

[calvinaco]

  1) TxDecoder Golang vs JSlib
       should decode to the same result:
     TypeError: Cannot read property 'length' of undefined
      at Object.fromByteArray (node_modules/base64-js/index.js:121:19)
      at Object.toBase64 (node_modules/@cosmjs/encoding/src/base64.ts:4:19)
      at Object.exports.getSignerInfoJson (lib/src/utils/txDecoder.ts:93:78)
      at /Users/hei/crypto-com/chain-jslib/lib/src/utils/txDecoder.ts:147:45
      at Array.map (<anonymous>)
      at Object.exports.getAuthInfoJson (lib/src/utils/txDecoder.ts:146:48)
      at TxDecoder.toCosmosJSON (lib/src/utils/txDecoder.ts:75:29)
      at Context.<anonymous> (lib/e2e/tx-decoder/compare.ts:101:81)
      at step (lib/e2e/tx-decoder/compare.ts:33:23)
      at Object.next (lib/e2e/tx-decoder/compare.ts:14:53)
      at fulfilled (lib/e2e/tx-decoder/compare.ts:5:58)
      at processTicksAndRejections (internal/process/task_queues.js:93:5)