Adds check for first query param for deltaBundleId (#277)

* Adds check for first query param for deltaBundleId

* Fix lint error

Author: rorydbain

app/middlewares/delta/deltaUrlToBlobUrl.js

@@ -16,10 +16,13 @@ const cachedBundleUrls = new Map();
 export default async function deltaUrlToBlobUrl(deltaUrl) {
   const client = DeltaPatcher.get(deltaUrl);
 
-  const deltaBundleId = client.getLastBundleId()
-    ? `&deltaBundleId=${client.getLastBundleId()}`
+  const lastBundleId = client.getLastBundleId();
+
+  const deltaBundleId = lastBundleId
+    ? `${lastBundleId.indexOf('?') === -1 ? '?' : '&'}deltaBundleId=${lastBundleId}`
     : '';
 
+
   const data = await fetch(deltaUrl + deltaBundleId);
   const bundle = await data.json();