fix(ImageMapper): unstable resource reference

Array getters by default return a copy of the underlying array.
labelOutlineThicknessArray is used as a key in a map to detect changes,
so use a reference to the underlying array instead of a copy.

Author: floryst

Sources/Rendering/OpenGL/ImageMapper/index.js

@@ -1367,7 +1367,7 @@ function vtkOpenGLImageMapper(publicAPI, model) {
   publicAPI.updatelabelOutlineThicknessTexture = (image) => {
     const labelOutlineThicknessArray = image
       .getProperty()
-      .getLabelOutlineThickness();
+      .getLabelOutlineThicknessByReference();
 
     const lTex = model._openGLRenderWindow.getGraphicsResourceForObject(
       labelOutlineThicknessArray