Fix NRE for gh 4267 (#7306)

Xamarin.Forms.Platform.iOS/ContextActionCell.cs

@@ -81,6 +81,9 @@ namespace Xamarin.Forms.Platform.iOS
 
 		public void Close()
 		{
+			if (_scroller == null)
+				return;
+
 			_scroller.ContentOffset = new PointF(0, 0);
 		}
 

Xamarin.Forms.Platform.iOS/Platform.cs

@@ -21,7 +21,7 @@ namespace Xamarin.Forms.Platform.iOS
 #if DEBUG
 				if (oldvalue != null && newvalue != null)
 				{
-					Log.Warning("Renderer", $"{bindable} already has a renderer attached to it: {oldvalue}. Please figure out why and then fix it.", nameof(oldvalue));
+					Log.Warning("Renderer", $"{bindable} already has a renderer attached to it: {oldvalue}. Please figure out why and then fix it.");
 				}
 #endif
 				var view = bindable as VisualElement;