Bug 182190 [StatusHandling] [Wizards] getControl assert on wizard page has no message
M6 If you forget to set the control on your wizard page our assert gives no feedback. We need an error message.
bundles/org.eclipse.jface/src/org/eclipse/jface/wizard/WizardDialog.java
IPageChangeProvider {
    /**
     * Image registry key for error message image (value <code>"dialog_title_error_image"</code>).
     */
    public static final String WIZ_IMG_ERROR = "dialog_title_error_image"; 
    
    private IWizard wizard;
    
    private ArrayList createdWizards = new ArrayList();
    
    private ArrayList nestedWizards = new ArrayList();
    
    private IWizardPage currentPage = null;
    	
    private long activeRunningOperations = 0;
    
    private String pageMessage;
    private int pageMessageType = IMessageProvider.NONE;
    private String pageDescription;
    
    private ProgressMonitorPart progressMonitorPart;
    private Cursor waitCursor;
    private Cursor arrowCursor;
    private MessageDialog windowClosingDialog;
    
    private Button backButton;
    private Button nextButton;
    private Button finishButton;
    private Button cancelButton;