Default edit handles are not shown on custom shapes

[JonasHelming]

I added a custom svg ("heart") and a ShapeTypeHint configuring resizable to true, but no edit handles are shown. Full reproducer: https://github.com/JonasHelming/glsp-examples/blob/34f0ea79fee784116e694d23994f4e8637ae8742/minimal/server/org.eclipse.glsp.example.minimal/src/main/java/org/eclipse/glsp/example/minimal/MinimalDiagramConfiguration.java#L38

Can be built exacty like the minimal example