fix(@angular-devkit/build-angular): allow empty scripts to be optimized

When using the internal JavaScript optimizer plugin for Webpack with an
empty script file provided via the `scripts` option, the build would fail.
This was because of a safety check that was checking whether the terser
result was falsy. Since an empty string is considered falsy, the build
considered the result to be an error. The safety check now will only trigger
if the terser result is not a string value to avoid this case.

(cherry picked from commit 2435b46)

packages/angular_devkit/build_angular/src/builders/browser/tests/options/scripts_spec.ts

@@ -27,6 +27,27 @@ describeBuilder(buildWebpackBrowser, BROWSER_BUILDER_INFO, (harness) => {
       expect(result?.success).toBe(true);
     });
 
+    it('processes an empty script when optimizing', async () => {
+      await harness.writeFile('src/test-script-a.js', '');
+
+      harness.useTarget('build', {
+        ...BASE_OPTIONS,
+        optimization: {
+          scripts: true,
+        },
+        scripts: ['src/test-script-a.js'],
+      });
+
+      const { result } = await harness.executeOnce();
+
+      expect(result?.success).toBe(true);
+
+      harness.expectFile('dist/scripts.js').toExist();
+      harness
+        .expectFile('dist/index.html')
+        .content.toContain('<script src="scripts.js" defer></script>');
+    });
+
     describe('shorthand syntax', () => {
       it('processes a single script into a single output', async () => {
         await harness.writeFile('src/test-script-a.js', 'console.log("a");');

packages/angular_devkit/build_angular/src/webpack/plugins/javascript-optimizer-worker.ts

@@ -227,7 +227,7 @@ async function optimizeWithTerser(
     },
   );
 
-  if (!result.code) {
+  if (typeof result.code !== 'string') {
     throw new Error('Terser failed for unknown reason.');
   }