Steps to Reproduce

1. load the attached file
2. cut C6 and past to A1

Current Result

java.lang.NullPointerException
at org.zkoss.zss.model.impl.SheetImpl.getConditionalFormattingStyle(SheetImpl.java:2314)
at org.zkoss.zss.ui.Spreadsheet$ExtraCtrl.getCellAttr(Spreadsheet.java:3699)
at org.zkoss.zss.ui.Spreadsheet$ExtraCtrl.getRangeAttrs(Spreadsheet.java:3552)
at org.zkoss.zss.ui.Spreadsheet.responseUpdateCell(Spreadsheet.java:3123)
at org.zkoss.zss.ui.Spreadsheet.updateCell(Spreadsheet.java:3092)
at org.zkoss.zss.ui.Spreadsheet.access$4400(Spreadsheet.java:233)
at org.zkoss.zss.ui.Spreadsheet$InnerModelEventDispatcher.onCellContentChange(Spreadsheet.java:2644)
at org.zkoss.zss.ui.Spreadsheet$InnerModelEventDispatcher.access$1400(Spreadsheet.java:2322)
at org.zkoss.zss.ui.Spreadsheet$InnerModelEventDispatcher$8.onEvent(Spreadsheet.java:2373)
at org.zkoss.zss.ui.ModelEventDispatcher.onEvent(ModelEventDispatcher.java:49)
at org.zkoss.zss.model.impl.EventQueueListenerAdaptor$WrappedListener.onEvent(EventQueueListenerAdaptor.java:107)
at org.zkoss.zk.ui.event.impl.DesktopEventQueue$QueueListener.onEvent(DesktopEventQueue.java:168)
at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:3165)
at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:3135)
at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:3077)
at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:138)
at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1846)
at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1618)
at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1321)

Expected Result

the cell pasted without errors