Merge branch 'master' into scroll_snap

src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs

@@ -151,7 +151,11 @@ namespace Avalonia.Controls
                     _content.Loaded += (s, e) =>
                     {
                         var composition = ElementComposition.GetElementVisual(_content);
-                        var compositor = composition!.Compositor;
+
+                        if(composition == null)
+                            return;
+
+                        var compositor = composition.Compositor;
                         composition.Opacity = 0;
 
                         var smoothRotationAnimation

src/Avalonia.Controls/TopLevel.cs

@@ -318,7 +318,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Occurs when physical Back Button is pressed or a back navigation has been requested.
         /// </summary>
-        public event EventHandler<RoutedEvent> BackRequested
+        public event EventHandler<RoutedEventArgs> BackRequested
         {
             add { AddHandler(BackRequestedEvent, value); }
             remove { RemoveHandler(BackRequestedEvent, value); }

src/iOS/Avalonia.iOS/TextInputResponder.cs

@@ -445,7 +445,7 @@ partial class AvaloniaView
 
         UITextPosition IUITextInput.BeginningOfDocument => _beginningOfDocument;
 
-        private int DocumentLength => _client.SurroundingText.Text.Length + (_markedText?.Length ?? 0);
+        private int DocumentLength => (_client.SurroundingText.Text?.Length ?? 0) + (_markedText?.Length ?? 0);
         UITextPosition IUITextInput.EndOfDocument => new AvaloniaTextPosition(DocumentLength);
 
         UITextRange IUITextInput.MarkedTextRange