Describe the bug
The calendar gets invisible when changing CalendarLayout at runtime

To Reproduce
Steps to reproduce the behavior:

1. Bind CalendarLayout to a property in the ViewModel
2. Set the default value to WeekLayout.Month
3. Add a command that changes the ViewModel property from WeekLayout.Month to WeekLayout.Week
4. The calendar days get invisible
5. If not, try to execute the command one or two more times (Sometimes other calendar properties changes cause the calendar to render correctly).

Expected behavior
The calendar changes its layout from Month to Week and it's visible

Screenshots

Version information:

• Plugin version: 1.4.5304
• Xamarin.Forms version: 5.0.0.2012
• Platform: Android