fixup! fix(core): correctly check for typeof of undefined in `ngDev…

…Mode` check

packages/core/test/enable_prod_mode_spec.ts

@@ -0,0 +1,19 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {enableProdMode} from '@angular/core';
+
+
+describe('enableProdMode', () => {
+  it(`should set 'ngDevMode' to false when 'ngDevMode' is undefined`, () => {
+    const global = globalThis as typeof globalThis & {'ngDevMode': unknown};
+    global.ngDevMode = undefined;
+    enableProdMode();
+    expect(global.ngDevMode).toBeFalse();
+  });
+});