java.lang.NullPointerException at org.netbeans.modules.webpreview.HTMLWebPreviewable$HTMLWebPreviewableImpl.onAttach(HTMLWebPreviewable.java:124) at org.netbeans.modules.webpreview.WebPreviewControler$1.propertyChange(WebPreviewControler.java:104) at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339) at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276) at org.netbeans.modules.webpreview.HTMLWebPreviewable$HTMLWebPreviewableImpl.setPreviewEnabled(HTMLWebPreviewable.java:94) at org.netbeans.modules.webpreview.HTMLPreviewAction.actionPerformed(HTMLPreviewAction.java:73) at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1995) at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2318) at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:387) at javax.swing.JToggleButton$ToggleButtonModel.setPressed(JToggleButton.java:291) at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:236) at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272) at java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:272) at java.awt.Component.processMouseEvent(Component.java:6263) at javax.swing.JComponent.processMouseEvent(JComponent.java:3255) at java.awt.Component.processEvent(Component.java:6028) at java.awt.Container.processEvent(Container.java:2041) at java.awt.Component.dispatchEventImpl(Component.java:4630) at java.awt.Container.dispatchEventImpl(Container.java:2099) at java.awt.Component.dispatchEvent(Component.java:4460) at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4574) at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:4238) at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4168) at java.awt.Container.dispatchEventImpl(Container.java:2085) at java.awt.Window.dispatchEventImpl(Window.java:2475) at java.awt.Component.dispatchEvent(Component.java:4460) at java.awt.EventQueue.dispatchEvent(EventQueue.java:599) at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:133) at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269) at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184) at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169) at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161) at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)