No windows is presented when trying to launch Mac app
## 🐛 Bug Report

I had the issue with the playground project where Mac app would launch, but be empty (no windows opened, no activity). I decided to make my own test project

Unfortunately, there is no real documentation, only one page on Presenters which is not clear enough (IMO) and the simple test project described here doesn't contain mac example:
https://www.mvvmcross.com/documentation/tutorials/tipcalc/a-xamarinios-ui-project

I will link my project below, it starts and just like Playground app doesn't have any windows, but at least there is some activity in console:

```
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Primary start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: FirstChance start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Platform services
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: MvvmCross settings start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Singleton Cache start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: ViewDispatcher start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Bootstrap actions
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: StringToTypeParser start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: FillableStringToTypeParser start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: PluginManagerFramework start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Create App
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: NavigationService
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Load navigation routes
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: App start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Application Initialize - On background thread
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: ViewModelTypeFinder start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: ViewsContainer start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Lookup Dictionary start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Views start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: CommandCollectionBuilder start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: NavigationSerializer start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: InpcInterception start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: InpcInterception start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: LastChance start
2020-07-10 10:46:41 [TRACE] (MvvmCross.Core.MvxSetup) Setup: Secondary end
2020-07-10 10:46:41 [TRACE] (MvvmCross.Logging.MvxLog) AppStart: Application Startup - On UI thread
2020-07-10 10:46:41 [TRACE] (MvvmCross.Logging.MvxLog) Hint ignored in default MvxAppStart
2020-07-10 10:46:41 [TRACE] (MvvmCross.Logging.MvxLog) MacNavigation
```

[MvvmCrossTest.zip](https://github.com/MvvmCross/MvvmCross/files/4901787/MvvmCrossTest.zip)


### Expected behavior

App launches

### Reproduction steps

1. Unzip my project
2. Launch it

### Configuration

**Version:** 6.4.2

**Platform:** 
- [ ] :iphone: iOS
- [ ] :robot: Android
- [ ] :checkered_flag: WPF
- [ ] :earth_americas: UWP
- [ 10.15 ] :apple: MacOS
- [ ] :tv: tvOS
- [ ] :monkey: Xamarin.Forms
