Error when adding @angular/pwa: Invalid rule result: Instance of class Promise

After I create a project with Ionic 5 CLI, I tried to publish project as PWA and follow instruction in document

I run this command in project

ng add @angular/pwa

which shows result in terminal

Installing packages for tooling via npm.
+ @angular/pwa@0.801.2
added 11 packages from 10 contributors and audited 51528 packages in 15.415s
found 759 vulnerabilities (2 low, 4 moderate, 753 high)
  run `npm audit fix` to fix them, or `npm audit` for details
Installed packages for tooling via npm.
Invalid rule result: Instance of class Promise.

The last line: Invalid rule result: Instance of class Promise. , show in red.

Does it suppose to be like this?

Here is my Ionic Info:

Ionic:

   Ionic CLI                     : 5.2.3 (/usr/local/lib/node_modules/ionic)
   Ionic Framework               : @ionic/angular 4.0.0
   @angular-devkit/build-angular : 0.12.3
   @angular-devkit/schematics    : 7.2.3
   @angular/cli                  : 7.2.3
   @ionic/angular-toolkit        : 1.2.3

Cordova:

   Cordova CLI       : 9.0.0 (cordova-lib@9.0.1)
   Cordova Platforms : none
   Cordova Plugins   : no whitelisted plugins (0 plugins total)

Utility:

   cordova-res : 0.6.0 
   native-run  : 0.2.5 (update available: 0.2.8)

System:

   Android SDK Tools : 26.1.1 (/Users/teerasejjiraphatchandej/Library/Android/sdk)
   ios-deploy        : 1.9.4
   ios-sim           : 6.1.2
   NodeJS            : v10.16.0 (/usr/local/bin/node)
   npm               : 6.10.1
   OS                : macOS Mojave
   Xcode             : Xcode 10.2.1 Build version 10E1001