title: SwiftUI ProgressView not showing when inside List
body: <p>In the following simple example you will find that the first time you tap <code>Toggle Loading</code> the <code>ProgressView</code> is shown as it should, but the second time (3rd tap) it's not.
  It seems to be caused by the surrounding List.</p>
  <p>Any ideas what the issue is and how to make it work?</p>
  <pre class="lang-swift prettyprint-override"><code>struct ContentView: View {
  
      @State private var isLoading = false
  
      var body: some View {
          List {
              if isLoading {
                  HStack(alignment: .center, spacing: 10) {
                      ProgressView()
                      Text(&quot;Loading&quot;)
                  }
              } else {
                  Text(&quot;Not Loading&quot;)
              }
  
              Button(&quot;Toggle Loading&quot;) {
                  isLoading.toggle()
              }
          }
      }
  }
  </code></pre>