fix: sanity checks on ccxt responses

lib/plugins/ticker/ccxt.js

@@ -8,6 +8,14 @@ const RETRIES = 2
 
 const tickerObjects = {}
 
+// This is probably fixed on upstream ccxt
+// but we need to udpate node to get on the latest version
+const sanityCheckRates = (ask, bid, tickerName) => {
+  if (new BN(0).eq(ask) || new BN(0).eq(bid)) {
+    throw new Error(`Failure fetching rates for ${tickerName}`)
+  }
+}
+
 function ticker (fiatCode, cryptoCode, tickerName) {
   if (!tickerObjects[tickerName]) {
     tickerObjects[tickerName] = new ccxt[tickerName]({
@@ -45,12 +53,15 @@ function getCurrencyRates (ticker, fiatCode, cryptoCode) {
     }
     const symbol = buildMarket(fiatCode, cryptoCode, ticker.id)
     return ticker.fetchTicker(symbol)
-      .then(res => ({
-        rates: {
-          ask: new BN(res.ask),
-          bid: new BN(res.bid)
+      .then(res => {
+        sanityCheckRates(res.ask, res.bid, cryptoCode)
+        return {
+          rates: {
+            ask: new BN(res.ask),
+            bid: new BN(res.bid)
+          }
         }
-      }))
+    })
   } catch (e) {
     return Promise.reject(e)
   }