java.lang.AssertionError
   at org.netbeans.modules.web.common.api.browser.BrowserSupport$1.propertyChange(BrowserSupport.java:132)
   at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:339)
   at java.beans.PropertyChangeSupport.firePropertyChange(PropertyChangeSupport.java:276)
   at org.netbeans.modules.web.common.api.browser.WebBrowsers.fireDefaultBrowserChange(WebBrowsers.java:179)
   at org.netbeans.modules.web.common.api.browser.WebBrowsers.access$100(WebBrowsers.java:64)
   at org.netbeans.modules.web.common.api.browser.WebBrowsers$2.preferenceChange(WebBrowsers.java:127)
   at java.util.prefs.AbstractPreferences$EventDispatchThread.run(AbstractPreferences.java:1475)