Bugfix
If you create a singleton in a module, it can be deleted in the instance browser. After that, "pretty much" everything is broken. To repair this, you have to delete the corresponding singleton annotation in the module and create it again.
Target state
Objects that were created as singletons should not be able to be deleted - unless the singleton annotation is deleted in the module.
Test
- com.top_logic.demo/target/test-classes/test/com/top_logic/demo/scripted/model/TestPreventSingletonDeletion.script.xml