message: fix(core): ensure that `ngI18nClosureMode` is guarded
  If the `ngI18nClosureMode` global check actually makes it
  through to the runtime, then checks for its existence should
  be guarded to prevent `Reference undefined` errors in strict
  mode.
  (Normally, it is stripped out by dead code elimination during
  build optimization.)
  PR Close
diff: @@ -49,7 +49,8 @@ export function _localeFactory(locale?: string): string {
  * * Ivy enabled: use `$localize.locale`
  */
  export function getGlobalLocale(): string {
  - if (ngI18nClosureMode && typeof goog !== 'undefined' && goog.LOCALE !== 'en') {
  + if (typeof ngI18nClosureMode !== 'undefined' && ngI18nClosureMode &&
  + typeof goog !== 'undefined' && goog.LOCALE !== 'en') {
  // * The default `goog.LOCALE` value is `en`, while Angular used `en-US`.
  // * In order to preserve backwards compatibility, we use Angular default value over
  // Closure Compiler's one.
  