[Bug] Memory leak in WidgetState

[Antti-Palola]

Bug description

Instantiating for example a plane widget and properly removing the widget and its manager with delete leaks memory.

Steps to reproduce

• Instantiate a widget
• Delete widget
• Widget state leaks memory

Detailed Behavior

Loaded widgets three times, notice the groups of 3 distinct size, which are all different different states when loading the same view three times.

Cause would seem to be

vtk-js/Sources/Widgets/Core/WidgetState/index.js

Line 57 in 21534d1

subscriptions.push(model.nestedStates[i].onModified(publicAPI.modified));

that pushes a callback in unbindState

Expected Behavior

No memory leaks

Environment

• vtk.js version: main of 22.4.2024 (21534d1)
• Browsers: Chrome
• OS: Mac OS 14.3.