Getting this error after upgrading my global Angular CLI to version 1.7.3(not sure exactly is breaking the build). Web pack seems not understand path reference any more.
ERROR in ./src/app/app.component.css
(Emitted value instead of an instance of Error) CssSyntaxError: C:\Users\kkehinde\Documents\WebStorm\Admin\src\assets\css\theme-default.css:7102:19: Can't resolve '../img/filetree/code.png'
in 'C:\Users\kkehinde\Documents\WebStorm\Admin\src\app'
  7100 | }
  7101 | li.ext_xml {
> 7102 |   background: url(../img/filetree/code.png) left top no-repeat;
       |                   ^
  7103 | }
  7104 | li.ext_zip {
ERROR in ./src/app/app.component.css
(Emitted value instead of an instance of Error) CssSyntaxError: C:\Users\kkehinde\Documents\WebStorm\Admin\src\assets\css\theme-default.css:7105:19: Can't resolve '../img/filetree/zip.png' in 'C:\Users\kkehinde\Documents\WebStorm\Admin\src\app'
  7103 | }
  7104 | li.ext_zip {
> 7105 |   background: url(../img/filetree/zip.png) left top no-repeat;
       |                   ^
  7106 | }
  7107 | /* END Filetree */
My Package.json is below, I added locked down node-sass to version 4.7.2 as someone suggested that that was what is breaking the webpack build but still getting same above error.
{
  "name": "admin",
  "version": "0.0.0",
  "license": "MIT",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^4.4.4",
    "@angular/cdk": "^2.0.0-beta.12",
    "@angular/common": "^4.0.0",
    "@angular/compiler": "^4.0.0",
    "@angular/core": "^4.0.0",
    "@angular/forms": "^4.0.0",
    "@angular/http": "^4.0.0",
    "@angular/material": "^2.0.0-beta.12",
    "@angular/platform-browser": "^4.0.0",
    "@angular/platform-browser-dynamic": "^4.0.0",
    "@angular/router": "^4.0.0",
    "angular2-notifications": "^0.7.8",
    "core-js": "^2.4.1",
    "ng2-progressbar": "^1.3.0",
    "ngx-progressbar": "^2.0.8",
    "rxjs": "^5.1.0",
    "zone.js": "^0.8.4"
  },
  "devDependencies": {
    "@angular/cli": "^1.5.2",
    "@angular/compiler-cli": "^4.0.0",
    "@angular/language-service": "^4.0.0",
    "@types/jasmine": "~2.5.53",
    "@types/jasminewd2": "~2.0.2",
    "@types/node": "~6.0.60",
    "codelyzer": "~3.0.1",
    "jasmine-core": "~2.6.2",
    "jasmine-spec-reporter": "~4.1.0",
    "karma": "~1.7.0",
    "karma-chrome-launcher": "~2.1.1",
    "karma-cli": "~1.0.1",
    "karma-coverage-istanbul-reporter": "^1.2.1",
    "karma-jasmine": "~1.1.0",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.1.2",
    "ts-node": "~3.0.4",
    "tslint": "~5.3.2",
    "typescript": "~2.3.3",
    "node-sass": "4.7.2"
  }
}