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
}
        case IDialogConstants.NEXT_ID: {
            nextPressed();
            break;
        }
        case IDialogConstants.FINISH_ID: {
            finishPressed();
            break;
        }
        
        }
    }
    /**
     * Calculates the difference in size between the given
     * page and the page container. A larger page results 
     * in a positive delta.
     *
     * @param page the page
     * @return the size difference encoded
     *   as a <code>new Point(deltaWidth,deltaHeight)</code>
     */
    private Point calculatePageSizeDelta(IWizardPage page) {
        Control pageControl = page.getControl();
        if (pageControl == null) {
			
            return new Point(0, 0);
		}
        Point contentSize = pageControl.computeSize(SWT.DEFAULT, SWT.DEFAULT,
                true);
        Rectangle rect = pageContainerLayout.getClientArea(pageContainer);