2-19进销管理系统报错

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at java.util.Hashtable.get(Unknown Source)
at javax.swing.KeyboardManager.registerMenuBar(Unknown Source)
at javax.swing.JMenuBar.addNotify(Unknown Source)
at java.awt.Container.addNotify(Unknown Source)
at javax.swing.JComponent.addNotify(Unknown Source)
at javax.swing.plaf.metal.MetalTitlePane.addNotify(Unknown Source)
at java.awt.Container.addNotify(Unknown Source)
at javax.swing.JComponent.addNotify(Unknown Source)
at java.awt.Container.addNotify(Unknown Source)
at javax.swing.JComponent.addNotify(Unknown Source)
at javax.swing.JRootPane.addNotify(Unknown Source)
at java.awt.Container.addNotify(Unknown Source)
at java.awt.Window.addNotify(Unknown Source)
at java.awt.Frame.addNotify(Unknown Source)
at java.awt.Window.pack(Unknown Source)
at sun.awt.im.CompositionArea.<init>(Unknown Source)
at sun.awt.im.CompositionAreaHandler.createCompositionArea(Unknown Source)
at sun.awt.im.CompositionAreaHandler.inputMethodTextChanged(Unknown Source)
at sun.awt.im.CompositionAreaHandler.processInputMethodEvent(Unknown Source)
at sun.awt.im.InputMethodContext.dispatchEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)