Issue on Navigating back Master Details Page in Xamarin forms MVVM prism using unity

Hi, I've attached a small project in which I'm currently facing the issue.
I've one Page it navigates to MasterDetail Page. MasterDetail Consist a Page1 in detail , there is one button which navigates to page2. Now when I navigate back then it navigates to Page1 but the MasterDetail Page is not available now..