fix(@angular/cli): fix empty style urls

Author: sumitarora

packages/@ngtools/webpack/src/loader.ts

@@ -361,7 +361,7 @@ function _getResourcesUrls(refactor: TypeScriptFileRefactor): string[] {
         const arr = <ts.ArrayLiteralExpression[]>(
           refactor.findAstNodes(node, ts.SyntaxKind.ArrayLiteralExpression, false));
         if (!arr || arr.length == 0 || arr[0].elements.length == 0) {
-          return;
+          return acc;
         }
 
         arr[0].elements.forEach((element: ts.Expression) => {

tests/e2e/tests/build/styles/empty-style-urls.ts

@@ -0,0 +1,24 @@
+import { writeMultipleFiles } from '../../../utils/fs';
+import { ng } from '../../../utils/process';
+
+
+export default function () {
+
+  return Promise.resolve()
+    // Write assets.
+    .then(_ => writeMultipleFiles({
+      './src/app/app.component.ts': `
+        import { Component } from '@angular/core';
+
+        @Component({
+          selector: 'app-root',
+          templateUrl: './app.component.html',
+          styleUrls: []
+        })
+        export class AppComponent {
+          title = 'app';
+        }
+      `
+    }))
+    .then(() => ng('build'));
+}