NPE in TokenSequencePreservingPartialParsingHelper.isBrokenPreviousState

java.lang.NullPointerException
	at org.eclipse.xtext.xbase.parser.TokenSequencePreservingPartialParsingHelper.isBrokenPreviousState(TokenSequencePreservingPartialParsingHelper.java:143)
	at org.eclipse.xtext.xbase.parser.TokenSequencePreservingPartialParsingHelper.reparse(TokenSequencePreservingPartialParsingHelper.java:74)
	at org.eclipse.xtext.parser.antlr.AbstractAntlrParser.doReparse(AbstractAntlrParser.java:138)
	at org.eclipse.xtext.parser.AbstractParser.reparse(AbstractParser.java:50)
	at org.eclipse.xtext.resource.XtextResource.update(XtextResource.java:253)
	at org.eclipse.xtext.ui.editor.reconciler.XtextDocumentReconcileStrategy.doReconcile(XtextDocumentReconcileStrategy.java:150)
	at org.eclipse.xtext.ui.editor.reconciler.XtextDocumentReconcileStrategy.reconcile(XtextDocumentReconcileStrategy.java:67)
	at org.eclipse.xtext.ui.editor.reconciler.XtextReconciler.doRun(XtextReconciler.java:442)
	at org.eclipse.xtext.ui.editor.reconciler.XtextReconciler.access$3(XtextReconciler.java:422)
	at org.eclipse.xtext.ui.editor.reconciler.XtextReconciler$1.process(XtextReconciler.java:363)
	at org.eclipse.xtext.ui.editor.reconciler.XtextReconciler$1.process(XtextReconciler.java:1)
	at org.eclipse.xtext.util.concurrent.IUnitOfWork$Void.exec(IUnitOfWork.java:37)
	at org.eclipse.xtext.resource.OutdatedStateManager.exec(OutdatedStateManager.java:98)
	at org.eclipse.xtext.ui.editor.model.XtextDocument$XtextDocumentLocker.modify(XtextDocument.java:428)
	at org.eclipse.xtext.ui.editor.model.XtextDocument.internalModify(XtextDocument.java:162)
	at org.eclipse.xtext.ui.editor.reconciler.XtextReconciler.run(XtextReconciler.java:360)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)

@szarnekow do you have any idea what could cause this. and should there be a null guard?

Start in TokenSequencePreservingPartialParsingHelper.java at isBrokenPreviousState, line 143, then trace its callers through reparse and AbstractAntlrParser.doReparse. Determine which state is null and whether the failure comes from the partial-parsing path. Done means the reported reconciliation path no longer raises this NPE, with the appropriate fix confirmed.