**java.lang.NullPointerException: Cannot invoke "org.eclipse.sirius.business.api.session.Session.getSelectedViewpoints(boolean)" because "this.session" is null**
at org.eclipse.sirius.diagram.business.internal.sync.DDiagramSynchronizer.activateInitialLayers(DDiagramSynchronizer.java:289)
at org.eclipse.sirius.diagram.business.internal.sync.DDiagramSynchronizer.initDiagram(DDiagramSynchronizer.java:239)
at org.eclipse.sirius.diagram.business.internal.dialect.DiagramDialectServices.createRepresentation(DiagramDialectServices.java:162)
at org.eclipse.sirius.diagram.business.internal.dialect.DiagramDialectServices.createRepresentation(DiagramDialectServices.java:174)
at org.eclipse.sirius.business.internal.dialect.DialectManagerImpl.createRepresentation(DialectManagerImpl.java:144)
at org.eclipse.sirius.business.api.dialect.command.CreateRepresentationCommand.doExecute(CreateRepresentationCommand.java:117)
at org.eclipse.emf.transaction.RecordingCommand.execute(RecordingCommand.java:135)
at org.eclipse.emf.workspace.EMFCommandOperation.doExecute(EMFCommandOperation.java:119)
at org.eclipse.emf.workspace.AbstractEMFOperation.execute(AbstractEMFOperation.java:150)
at org.eclipse.core.commands.operations.DefaultOperationHistory.execute(DefaultOperationHistory.java:496)
at org.eclipse.emf.workspace.impl.WorkspaceCommandStackImpl.doExecute(WorkspaceCommandStackImpl.java:208)
at fr.obeo.dsl.viewpoint.collab.api.editingdomain.NonDirtyingCapableWorkspaceCommandStack.doExecute(NonDirtyingCapableWorkspaceCommandStack.java:69)
at org.eclipse.emf.transaction.impl.AbstractTransactionalCommandStack.execute(AbstractTransactionalCommandStack.java:165)
at org.eclipse.emf.transaction.impl.AbstractTransactionalCommandStack.execute(AbstractTransactionalCommandStack.java:219)
at fr.pacman.start.ui.util.SiriusUtil.createRepresentation(SiriusUtil.java:450)
at fr.pacman.start.ui.util.SiriusUtil.createRepresentations(SiriusUtil.java:366)
at fr.pacman.start.ui.util.SiriusUtil.createModelingResources(SiriusUtil.java:143)
at fr.pacman.start.ui.util.SiriusUtil.addModelingResources(SiriusUtil.java:102)
at fr.pacman.start.ui.AcceleoGenrateStartAction.addEMFNatureToProjectModel(AcceleoGenrateStartAction.java:331)
at fr.pacman.start.ui.AcceleoGenrateStartAction.access$4(AcceleoGenrateStartAction.java:308)
at fr.pacman.start.ui.AcceleoGenrateStartAction$1.run(AcceleoGenrateStartAction.java:103)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
Dont voici la stackTrace :