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
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Label;
import org.eclipse.swt.widgets.Layout;
import org.eclipse.swt.widgets.Shell;
/**
 * A dialog to show a wizard to the end user. 
 * <p>
 * In typical usage, the client instantiates this class with 
 * a particular wizard. The dialog serves as the wizard container
 * and orchestrates the presentation of its pages.
 * <p>
 * The standard layout is roughly as follows: 
 * it has an area at the top containing both the
 * wizard's title, description, and image; the actual wizard page
 * appears in the middle; below that is a progress indicator
 * (which is made visible if needed); and at the bottom
 * of the page is message line and a button bar containing 
 * Help, Next, Back, Finish, and Cancel buttons (or some subset).
 * </p>
 * <p>
 * Clients may subclass <code>WizardDialog</code>, although this
 * is rarely required.
 * </p>
 */
public class WizardDialog extends TitleAreaDialog implements IWizardContainer2,