title: SwiftUI - NavigationBar not showing in Modal NavigationView
body: <p>Trying to make a modal that's similar to the "Create Event" modal in Apple's Calendar app. I've got my modal successfully showing using the following code in a parent NavigationView:</p>
  
  <pre><code>.navigationBarItems(trailing:
                      Button(action: {
                          self.isModal = true
                          }) {
                          Image(systemName: "plus").sheet(isPresented: $isModal, content: {
                              EventCreate(showModal: self.$isModal)
                          })
                      }
              )
  </code></pre>
  
  <p>The modal shows successfully, but I can't get a NavigationBar to show in the modal, which looks like this:</p>
  
  <pre><code>struct EventCreate: View {
  
      @Binding var showModal: Bool
  
      @State var event = Event(id: 0, title: "", description: "", location: "", start: Date(), end: Date(), cancelled: false, public_occurrence: false, created: "", last_updated: "", guests: -1)
  
      var body: some View {
          NavigationView {
              Form{
                  Section {
                      TextField("Title", text: $event.title)
                      TextField("Location", text: $event.location)
                  }
                  Section {
                      DatePicker(selection: $event.start, label: { Text("Start") })
                      DatePicker(selection: $event.end, label: { Text("End") })
                  }
              }
          }
          .navigationBarTitle(Text("Create Event"), displayMode: .inline)
          .navigationBarItems(leading:
              Button("Close") {
                  self.showModal = false
          })
  
      }
  }
  </code></pre>
  
  <p>The app builds, and the Form is displayed, but the NavigationView doesn't:
  <a href="https://i.stack.imgur.com/o7CJv.png" rel="noreferrer"><img src="https://i.stack.imgur.com/o7CJv.png" alt="Screenshot of missing view"></a></p>
  
  <p>How can I make this show? Or is there another view I should be using instead of NavigationView</p>