fix(wasm_imagebrush): Fixed a bug when ImageBrush on shapes was dynam…

…ically changing on Wasm: the previous image were not removed from the SVG pattern.

src/Uno.UI/UI/Xaml/Media/ImageBrush.wasm.cs

@@ -87,17 +87,17 @@ void OnImageSourceChanged(DependencyObject dependencyobject, DependencyPropertyC
 
 			void OnStretchChanged(DependencyObject dependencyobject, DependencyPropertyChangedEventArgs args)
 			{
-				SetPreserveAspectRatio();
+				preserveAspectRatio = SetPreserveAspectRatio();
 			}
 
 			void OnAlignmentChanged(DependencyObject dependencyobject, DependencyPropertyChangedEventArgs args)
 			{
-				SetPreserveAspectRatio();
+				preserveAspectRatio = SetPreserveAspectRatio();
 			}
 
 			void OnTargetLayoutUpdated(object sender, object e)
 			{
-				SetPreserveAspectRatio();
+				preserveAspectRatio = SetPreserveAspectRatio();
 			}
 
 			subscriptionDisposable.Disposable = ImageSource?.Subscribe(OnSourceOpened);
@@ -120,9 +120,14 @@ void OnSourceOpened(ImageData data)
 							("height", "100%"),
 							("preserveAspectRatio", preserveAspectRatio),
 							("href", _imageUri)
-
 						);
 
+						// Clear any previous image, if any
+						foreach(var previousChild in pattern.GetChildren())
+						{
+							pattern.RemoveChild(previousChild);
+						}
+
 						pattern.AddChild(image);
 
 						if (Stretch == Stretch.None)