Bug 48364 PreferenceDialog can reopen empty
20031209 When you close the Preferences dialog with an entry other than the default selected you will get an empty entry in the dialog when you reopen STEPS 1) Open the preferences dialog 2) Select the Appearances page 3) Close the dialog 4) Reopen - Workbench will be selected and the contents will be empty
bundles/org.eclipse.jface/src/org/eclipse/jface/preference/PreferenceContentProvider.java
public Object getParent(Object element) {
		return null;
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.viewers.ITreeContentProvider#hasChildren(java.lang.Object)
	 */
	public boolean hasChildren(Object element) {
		return getChildren(element).length > 0;
	}
	/** 
	 * @param inputElement must be an instance of <code>PreferenceManager</code>.
	 * @see org.eclipse.jface.viewers.IStructuredContentProvider#getElements(java.lang.Object)
	 */
	public Object[] getElements(Object inputElement) {
        return getChildren(((PreferenceManager)inputElement).getRoot());
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.viewers.IContentProvider#dispose()
	 */
	public void dispose() {
		
	}
	/* (non-Javadoc)
	 * @see org.eclipse.jface.viewers.IContentProvider#inputChanged(org.eclipse.jface.viewers.Viewer, java.lang.Object, java.lang.Object)
	 */
	public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
		
	}
}