Crash report: `Error: invalid BigNumber string (argument="value", value="erc721", code=INVALID_ARGUMENT, version=bignumber/5.6.0)`

URL

https://app.uniswap.org/#/swap?chain=mainnet

swap state

{
  "INPUT": {
    "currencyId": "ETH"
  },
  "OUTPUT": {
    "currencyId": null
  },
  "independentField": "INPUT",
  "typedValue": "",
  "recipient": null
}

Error

Error: invalid BigNumber string (argument="value", value="erc721", code=INVALID_ARGUMENT, version=bignumber/5.6.0)

Stacktrace

Error: invalid BigNumber string (argument="value", value="erc721", code=INVALID_ARGUMENT, version=bignumber/5.6.0)
    at e.value (https://app.uniswap.org/static/js/3.41edfc8a.chunk.js:2:83145)
    at e.value (https://app.uniswap.org/static/js/3.41edfc8a.chunk.js:2:83289)
    at e.value (https://app.uniswap.org/static/js/3.41edfc8a.chunk.js:2:83368)
    at Function.value (https://app.uniswap.org/static/js/3.41edfc8a.chunk.js:2:173013)
    at Qn (https://app.uniswap.org/static/js/main.19d4c78b.chunk.js:1:365204)
    at Hn (https://app.uniswap.org/static/js/main.19d4c78b.chunk.js:1:364034)
    at https://app.uniswap.org/static/js/main.19d4c78b.chunk.js:1:366279
    at Zn (https://app.uniswap.org/static/js/main.19d4c78b.chunk.js:1:366502)
    at oa (https://app.uniswap.org/static/js/3.41edfc8a.chunk.js:2:1938523)
    at za (https://app.uniswap.org/static/js/3.41edfc8a.chunk.js:2:1948090)

Device data

{
  "ua": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.54 Safari/537.36",
  "browser": {
    "name": "Chrome",
    "version": "101.0.4951.54",
    "major": "101"
  },
  "engine": {
    "name": "Blink",
    "version": "101.0.4951.54"
  },
  "os": {
    "name": "Mac OS",
    "version": "10.15.7"
  },
  "device": {},
  "cpu": {}
}

Start by reproducing the crash at the supplied Uniswap swap URL with the recorded swap state, then trace the minified stack back to the corresponding source entry point. Identify why the value "erc721" reaches BigNumber parsing and add regression coverage demonstrating that the swap page no longer crashes.