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
page.getControl().setVisible(false);
			}
        }
    }
    /**
     * Creates the Previous and Next buttons for this wizard dialog.
     * Creates standard (<code>SWT.PUSH</code>) buttons and registers for their
     * selection events. Note that the number of columns in the button bar composite
     * is incremented. These buttons are created specially to prevent any space 
     * between them.
     *
     * @param parent the parent button bar
     * @return a composite containing the new buttons
     */
    private Composite createPreviousAndNextButtons(Composite parent) {
        
        ((GridLayout) parent.getLayout()).numColumns++;
        Composite composite = new Composite(parent, SWT.NONE);
        
        GridLayout layout = new GridLayout();
        layout.numColumns = 0; 
        layout.marginWidth = 0;
        layout.marginHeight = 0;
        layout.horizontalSpacing = 0;
        layout.verticalSpacing = 0;
        composite.setLayout(layout);
        GridData data = new GridData(GridData.HORIZONTAL_ALIGN_CENTER
                | GridData.VERTICAL_ALIGN_CENTER);
        composite.setLayoutData(data);
        composite.setFont(parent.getFont());