Uncaught exception: isUnlock is not a function

[katspaugh]

Bug description

Sentry: https://sentry.io/organizations/gnosis/issues/3732706691/?project=6769196&query=is%3Aunresolved&referrer=issue-stream

It's coming from this code: https://github.com/safe-global/web-core/blob/dev/src/utils/wallets.ts#L30-L33

Probably some versions of MetaMask don't support this method. We need to add a check that it exists.

  if (window.ethereum?._metamask?.isUnlocked) {
    return window.ethereum._metamask.isUnlocked()
  }