message: default carbon tracker address to null
diff: @@ -44,6 +44,9 @@ const networksAndAddresses = {
  tokenNetwork: {
  address: "0xa94ec9484BfC9aB8d3fD80eB2735f132d257a135", // npx hardhat deploy --network ovm_localhost
  },
  + carbonTracker: {
  + address: "",
  + },
  dao: {
  governor: {
  address: "0x251b0aEbbe9D3e5281a699f45517D80Dd938eDa0", // npx hardhat deploy --network ovm_localhost
  @@ -59,6 +62,9 @@ const networksAndAddresses = {
  tokenNetwork: {
  address: "0x0D4F2bbE6d6A035769A97C72BD8bBeBE2338C500", // deployed 2021-03-25 on arbitrum kovan v4
  },
  + carbonTracker: {
  + address: "",
  + },
  dao: {
  governor: {
  address: "0x630192Cc43eA176B7b52995e3Cd1594eaCbaa454", // deployed 2021-03-25 on arbitrum kovan v4
  @@ -74,6 +80,9 @@ const networksAndAddresses = {
  tokenNetwork: {
  address: "0xf7B361Fe2dE41Cd092D2c777D2136CB8E3C2B146", // deployed 2021-04-06
  },
  + carbonTracker: {
  + address: "",
  + },
  dao: {
  governor: {
  address: "0x7137EB87725D61d69e6543E7b498bC4780AF1608", // deployed 2021-04-06
  @@ -89,6 +98,9 @@ const networksAndAddresses = {
  tokenNetwork: {
  address: "0xDf582cE97A933f6987b19838985874E4434207A2", // deployed 2021-04-06
  },
  + carbonTracker: {
  + address: "",
  + },
  dao: {
  governor: {
  address: "0x6E21205682C80E6BD2d292561BA8b736186132ED", // deployed 2021-04-29
  