Fix a bug with Promise.catch() in PromiseMiddleware

The pending action will be modified and a newly created promise handler
will be returned.

This has (suddenly?) caused errors in tests because the catch() handlers defined in tests would be called before the one defined in PromiseMiddleware:

    const p = new Promise(...)

    const {payload} = store.dispatch({
      payload: new Promise(...),
      type: '...',
    })

    try {
      await payload
    } catch (err) {
      // this handler would be invoked before the catch handler in
      // PromiseMiddleware
    }

since the PromiseMiddleware adds a then-callback, followed by a
catch-callback.

packages/jsonrpc/src/redux.test.ts

@@ -225,6 +225,7 @@ describe('createActions', () => {
           error = err
         }
         expect(error!).toBeTruthy()
+        expect(store.getState().mapping.error).toMatch(/status code 500/)
         expect(store.getState().handler.error).toMatch(/status code 500/)
       })
     })

packages/redux/src/middleware/PromiseMiddleware.ts

@@ -24,21 +24,26 @@ export class PromiseMiddleware {
     if (!isPromise(payload)) {
       return next(action)
     }
-    const pendingAction = {
-      ...action,
-      status: 'pending',
-    }
-    // Propagate this action. Only attach listeners to the promise.
-    next(pendingAction)
 
-    payload
+    const promise = payload
     .then(result => {
       store.dispatch({
         ...action,
         payload: result,
         status: 'resolved',
       })
+      return result
     })
+
+    const pendingAction = {
+      ...action,
+      payload: promise,
+      status: 'pending',
+    }
+    // Propagate this action. Only attach listeners to the promise.
+    next(pendingAction)
+
+    promise
     .catch(err => {
       store.dispatch({
         ...action,