Ensure token amounts are in fixed notation (#9381)

* Ensure token amounts are in fixed notation

ui/app/pages/confirm-token-transaction-base/confirm-token-transaction-base.container.js

@@ -44,7 +44,7 @@ const mapStateToProps = (state, ownProps) => {
   const tokenData = getTokenData(data)
   const tokenValue = getTokenValueParam(tokenData)
   const toAddress = getTokenAddressParam(tokenData)
-  const tokenAmount = tokenData && calcTokenAmount(tokenValue, decimals).toString()
+  const tokenAmount = tokenData && calcTokenAmount(tokenValue, decimals).toFixed()
   const contractExchangeRate = contractExchangeRateSelector(state)
 
   return {

ui/app/selectors/confirm-transaction.js

@@ -160,12 +160,15 @@ export const sendTokenTokenAmountAndToAddressSelector = createSelector(
     let toAddress = ''
     let tokenAmount = '0'
 
+    // Token params here are ethers BigNumbers, which have a different
+    // interface than bignumber.js
     if (args && args.length) {
       toAddress = args[TOKEN_PARAM_TO]
       let value = args[TOKEN_PARAM_VALUE].toString()
 
       if (tokenDecimals) {
-        value = calcTokenAmount(value, tokenDecimals).toString()
+        // bignumber.js return value
+        value = calcTokenAmount(value, tokenDecimals).toFixed()
       }
 
       tokenAmount = roundExponential(value)