Fix onFlushTimeout timer not being cleared when upstream errors (#1616)

src/helpers.ts

@@ -355,6 +355,7 @@ export default class Helpers {
       let loadedOperations = 0
       timeoutRef = setTimeout(onFlushTimeout, flushInterval) // eslint-disable-line
 
+      try {
         for await (const operation of operationsStream) {
           timeoutRef.refresh()
           loadedOperations += 1
@@ -368,8 +369,10 @@ export default class Helpers {
             loadedOperations = 0
           }
         }
-
+      } finally {
         clearTimeout(timeoutRef)
+      }
+
       // In some cases the previos http call does not have finished,
       // or we didn't reach the flush bytes threshold, so we force one last operation.
       if (loadedOperations > 0) {