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
Control[] children = composite.getChildren();
            if (children.length > 0) {
                result = new Point(0, 0);
                for (int i = 0; i < children.length; i++) {
                    Point cp = children[i].computeSize(wHint, hHint, force);
                    result.x = Math.max(result.x, cp.x);
                    result.y = Math.max(result.y, cp.y);
                }
                result.x = result.x + 2 * marginWidth;
                result.y = result.y + 2 * marginHeight;
            } else {
                Rectangle rect = composite.getClientArea();
                result = new Point(rect.width, rect.height);
            }
            result.x = Math.max(result.x, minimumWidth);
            result.y = Math.max(result.y, minimumHeight);
            if (wHint != SWT.DEFAULT) {
				result.x = wHint;
			}
            if (hHint != SWT.DEFAULT) {
				result.y = hHint;
			}
            return result;
        }
        /**
         * Returns the client area for the given composite according to this layout.
         *
         * @param c the composite
         * @return the client area rectangle
         */