Fix occasional race-condition NPE if LanguageManager sends a change event
before htmlReady() triggers languageSelect to get created.

It's not immediately obvious how this could happen: LM synchronously
requires languages.json, so it has all the core languages before the ESB
module loads; extensions don't start loading until after htmlReady(), so
extension-added languages can't cause this. BUT prefs load async in between
module init and htmlReady(), and LanguageManager populates partially async
too since it needs to wait for CM modes to load dynamically. I thnik either
of those can trigger a LM event during the window where ESB would crash.
Merge pull request #8818 from adobe/pflynn/languageswitcher-npe

Fix occasional NPE in EditorStatusBar during startup