ng add breaks angular workspace config

[alan-agius4]

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

Yes

Description

Just a fresh install angular ivy enabled with PWA and Universal

🔬 Minimal Reproduction

ng new shiny-ivy-app --enable-ivy
ng add @angular/pwa --project project-name
ng add @nguniversal/express-engine --clientProject angular.io-example
ng serve --open

🔥 Exception or Error

Schema validation failed with the following errors:
Data path "" should have required property 'main'.

🌍 Your Environment

     _                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/
    

Angular CLI: 8.1.0
Node: 10.15.3
OS: win32 x64
Angular: 8.1.0
... animations, cli, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... platform-server, router, service-worker

Package                                    Version
--------------------------------------------------------------------
@angular-devkit/architect                  0.801.0
@angular-devkit/build-angular              0.801.0
@angular-devkit/build-optimizer            0.801.0
@angular-devkit/build-webpack              0.801.0
@angular-devkit/core                       8.1.0
@angular-devkit/schematics                 8.1.0
@angular/pwa                               0.801.0
@ngtools/webpack                           8.1.0
@nguniversal/express-engine                8.1.0
@nguniversal/module-map-ngfactory-loader   8.1.0
@schematics/angular                        8.1.0
@schematics/update                         0.801.0
rxjs                                       6.5.2
typescript                                 3.4.5
webpack                                    4.35.2

From angular/angular-cli#14990

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