ConcurrentModificationException in Notebook.getNotesInfo

java.util.ConcurrentModificationException
        at java.util.HashMap$EntrySpliterator.forEachRemaining(HashMap.java:1704)
        at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
        at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
        at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
        at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
        at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:566)
        at org.apache.zeppelin.notebook.Notebook.getNotesInfo(Notebook.java:654)
        at org.apache.zeppelin.socket.NotebookServer$4.handleUser(NotebookServer.java:666)
        at org.apache.zeppelin.socket.ConnectionManager.forAllUsers(ConnectionManager.java:371)
        at org.apache.zeppelin.socket.NotebookServer.broadcastNoteListUpdate(NotebookServer.java:663)
        at org.apache.zeppelin.socket.NotebookServer.inlineBroadcastNoteList(NotebookServer.java:657)
        at org.apache.zeppelin.socket.NotebookServer.broadcastNoteList(NotebookServer.java:676)
        at org.apache.zeppelin.rest.NotebookRestApi$3.onSuccess(NotebookRestApi.java:465)
        at org.apache.zeppelin.rest.NotebookRestApi$3.onSuccess(NotebookRestApi.java:461)
        at org.apache.zeppelin.service.NotebookService.cloneNote(NotebookService.java:270)
        at org.apache.zeppelin.rest.NotebookRestApi.cloneNote(NotebookRestApi.java:460)
        at sun.reflect.GeneratedMethodAccessor50.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory.lambda$static$0(ResourceMethodInvocationHandlerFactory.java:52)
        at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:124)