how to reproduce: create new diagram, create new element, store, open -> nothing left (might need a bit of "playing around" to trigger the error)

	at org.unicase.model.diagram.impl.mediagramimpl.restoreoldresources(mediagramimpl.java:572)
	at org.unicase.model.diagram.impl.mediagramimpl.savediagramlayout(mediagramimpl.java:611)
	at org.unicase.ui.unicasecommon.diagram.part.modeldiagrameditor$2.dorun(modeldiagrameditor.java:111)
	at org.unicase.workspace.util.unicasecommand.doexecute(unicasecommand.java:32)
	at org.eclipse.emf.transaction.recordingcommand.execute(recordingcommand.java:133)
	at org.eclipse.emf.common.command.basiccommandstack.execute(basiccommandstack.java:84)
	... 88 more