title: "ERROR in Cannot read property 'map' of undefined" after updating from Angular 7 to 8
body: <p>I have got a strange error after upgrading from Angular 7 to 8. Everytime I start the program with npm start the following error occurs: "ERROR in Cannot read property 'map' of undefined".</p>
  
  <p>There is no more information on the console, so I couldn't find where the cause is. Therefore I have tried to comment out every occurance of .map in my code. Unfortunately the same error occurs. Additionly I updated all dependencies, but nothing has worked.</p>
  
  <p>Has someone else got a similar problem after upgrading from 7 to 8?
  My package.json looks like this:</p>
  
  <pre><code>  "name": "test",
    "version": "0.0.0",
    "scripts": {
      "ng": "ng",
      "start": "ng serve",
      "build": "ng build",
      "test": "ng test",
      "lint": "ng lint",
      "e2e": "ng e2e"
    },
    "private": true,
    "dependencies": {
      "@angular/animations": "^8.2.14",
      "@angular/cdk": "^7.3.7",
      "@angular/common": "~8.2.14",
      "@angular/compiler": "^8.2.14",
      "@angular/core": "^8.2.14",
      "@angular/flex-layout": "^8.0.0-beta.27",
      "@angular/forms": "~8.2.14",
      "@angular/material": "^7.3.7",
      "@angular/platform-browser": "~8.2.14",
      "@angular/platform-browser-dynamic": "^8.2.14",
      "@angular/router": "~8.2.14",
      "@ngx-translate/core": "^11.0.1",
      "@ngx-translate/http-loader": "^4.0.0",
      "apollo-angular": "^1.8.0",
      "apollo-angular-link-http": "^1.9.0",
      "apollo-cache-inmemory": "^1.6.5",
      "apollo-client": "^2.6.8",
      "apollo-link": "^1.2.13",
      "core-js": "^2.6.11",
      "graphql": "^14.6.0",
      "graphql-tag": "^2.10.3",
      "hammerjs": "^2.0.8",
      "ng2-split-pane": "^1.4.0",
      "ng2-tooltip-directive": "^2.8.17",
      "ngx-infinite-scroll": "^8.0.1",
      "resize-observer-polyfill": "^1.5.1",
      "rxjs": "~6.5.4",
      "tslib": "^1.10.0",
      "typescript": "^3.6.4",
      "zone.js": "^0.10.2"
    },
    "devDependencies": {
      "@angular-devkit/build-angular": "^0.803.24",
      "@angular/cli": "^8.3.25",
      "@angular/compiler-cli": "^9.0.4",
      "@angular/language-service": "~8.2.14",
      "@types/jasmine": "~2.8.8",
      "@types/jasminewd2": "^2.0.8",
      "@types/node": "^12.11.1",
      "codelyzer": "^5.1.2",
      "jasmine-core": "~2.99.1",
      "jasmine-spec-reporter": "~4.2.1",
      "karma": "^4.4.1",
      "karma-chrome-launcher": "~2.2.0",
      "karma-coverage-istanbul-reporter": "^2.0.6",
      "karma-jasmine": "~1.1.2",
      "karma-jasmine-html-reporter": "^0.2.2",
      "protractor": "^5.4.3",
      "ts-node": "~7.0.0",
      "tslint": "~5.11.0"
    },
    "browser": {
      "fs": false,
      "os": false,
      "path": false
    }
  }
  </code></pre>
  
  <p>Console log:</p>
  
  <pre><code>&gt; ng serve
  
  0% compiling
  Compiling @angular/core : es2015 as esm2015
  10% building 3/3 modules 0 activei ｢wds｣: Project is running at http://localhost:4200/webpack-dev-server/
  i ｢wds｣: webpack output is served from /
  i ｢wds｣: 404s will fallback to //index.html
  
  chunk {main} main.js, main.js.map (main) 2.01 kB [initial] [rendered]
  chunk {polyfills} polyfills.js, polyfills.js.map (polyfills) 684 bytes [initial] [rendered]
  chunk {runtime} runtime.js, runtime.js.map (runtime) 6.15 kB [entry] [rendered]
  chunk {styles} styles.js, styles.js.map (styles) 35 kB [initial] [rendered]
  chunk {vendor} vendor.js, vendor.js.map (vendor) 340 kB [initial] [rendered]
  Date: 2020-02-29T17:32:51.227Z - Hash: 5c477ba64195de423e38 - Time: 3371ms
  
  ERROR in Cannot read property 'map' of undefined
  ** Angular Live Development Server is listening on localhost:4200, open your browser on http://localhost:4200/ **
  i ｢wdm｣: Failed to compile.
  </code></pre>