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
public Rectangle getClientArea(Composite c) {
            Rectangle rect = c.getClientArea();
            rect.x = rect.x + marginWidth;
            rect.y = rect.y + marginHeight;
            rect.width = rect.width - 2 * marginWidth;
            rect.height = rect.height - 2 * marginHeight;
            return rect;
        }
        /* (non-Javadoc)
         * Method declared on Layout.
         */
        public void layout(Composite composite, boolean force) {
            Rectangle rect = getClientArea(composite);
            Control[] children = composite.getChildren();
            for (int i = 0; i < children.length; i++) {
                children[i].setBounds(rect);
            }
        }
        /**
         * Lays outs the page according to this layout.
         *
         * @param w the control
         */
        public void layoutPage(Control w) {
            w.setBounds(getClientArea(w.getParent()));
        }
        /**
         * Sets the location of the page so that its origin is in the
         * upper left corner.
         *