Investigate domain model problems with AnnotationModel.getAnnotationIterator

the reference projects domain model tests with java 17 log

2021-09-22T16:21:23.0173736Z Running org.eclipse.xtext.example.domainmodel.ui.tests.HoverTest
2021-09-22T16:21:25.3159216Z ##[error]Exception in thread "Thread-434" java.lang.NullPointerException: Cannot invoke "org.eclipse.jface.text.source.IAnnotationModel.getAnnotationIterator()" because the return value of "java.util.Map.get(Object)" is null
2021-09-22T16:21:25.3246313Z 	at org.eclipse.jface.text.source.AnnotationModel.getAnnotationIterator(AnnotationModel.java:744)
2021-09-22T16:21:25.3249917Z 	at org.eclipse.jface.text.source.AnnotationModel.getAnnotationIterator(AnnotationModel.java:668)
2021-09-22T16:21:25.3253466Z 	at org.eclipse.jface.text.source.projection.ProjectionSummary.removeSummaries(ProjectionSummary.java:175)
2021-09-22T16:21:25.3261494Z 	at org.eclipse.jface.text.source.projection.ProjectionSummary.internalUpdateSummaries(ProjectionSummary.java:154)
2021-09-22T16:21:25.3265570Z 	at org.eclipse.jface.text.source.projection.ProjectionSummary$Summarizer.run(ProjectionSummary.java:74)

https://pipelines.actions.githubusercontent.com/VGbhG7MqInqDfxY0bKv0qAuPeX3d22owq0UvtAsHMpYjQuu8bd/_apis/pipelines/1/runs/730/signedlogcontent/36?urlExpires=2021-09-22T16%3A28%3A02.7410229Z&urlSigningMethod=HMACV1&urlSignature=d4HvLy8UJha61ajPs0uQGm4HwVT%2B9h2uBzvtXwQNb9k%3D

to be investigated: is this a problem on our side or a problem that is in platform or fixed in latest platform.
might also be a problem with codeminings

Start with the Java 17 domain model test log, especially HoverTest and the AnnotationModel.java stack trace through ProjectionSummary. Reproduce the failure and compare the behavior with the latest platform; determine whether the cause is in Xtext, the platform, or codemining. Done means identifying the owning component and documenting whether a current failure remains.