Add missing disposing check on packager

Xamarin.Forms.Platform.Android/VisualElementPackager.cs

@@ -69,6 +69,8 @@ namespace Xamarin.Forms.Platform.Android
 
 			_disposed = true;
 
+			if (disposing)
+			{
 				if (_renderer != null)
 				{
 					_renderer.ElementChanged -= OnElementChanged;
@@ -103,6 +105,7 @@ namespace Xamarin.Forms.Platform.Android
 					_renderer = null;
 				}
 			}
+		}
 
 		public void Load()
 		{