promise middleware: fix to correctly return an error promise on error.

src/store/promise-middleware.ts

@@ -1,6 +1,6 @@
 // Based on: https://github.com/acdlite/redux-promise/blob/master/src/index.js
 
-function isPromise(val: any) {
+function isPromise(val: any): val is Promise<any> {
   return val && typeof val.then === 'function';
 }
 
@@ -9,10 +9,12 @@ export default function promiseMiddleware({ dispatch }: any) {
     if (isPromise(action.payload)) {
       dispatch({ ...action, payload: undefined });
 
-      return action.payload.then(
-        (result: any) => dispatch({ ...action, payload: result }),
-        (error: Error) => dispatch({ ...action, payload: error, error: true })
-      );
+      return action.payload
+        .then((result: any) => dispatch({ ...action, payload: result }))
+        .catch((error: Error) => {
+          dispatch({ ...action, payload: error, error: true });
+          return Promise.reject(error);
+        });
     } else {
       return next(action);
     }