macOS: fix crash on activating main window (fix #1212) (PR #1213)
macOS: fix crash on activating main window (fix #1212) (PR #1213)

```
Uncaught Exception:
TypeError: Cannot read property 'show' of undefined
at App.<anonymous> (/src/main.ts:177:18)
```

Seems like an oversight of the recent refactor.

* macOS: fix crash on activating main window (fix #1210)
* Eliminate need for global mainWindow, refactor widevine / non-widevine events (#1218)

Co-authored-by: Adam Weeden <9240ef2ead64a85c930552677607c6c0348da40b@gmail.com>
jiahaog/Nativefier,jiahaog/Nativefier,jiahaog/Nativefier