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
stopped(state);
			}
        }
    }
    /**
     * Saves the enabled/disabled state of the given control in the
     * given map, which must be modifiable.
     *
     * @param w the control, or <code>null</code> if none
     * @param h the map (key type: <code>String</code>, element type:
     *   <code>Boolean</code>)
     * @param key the key
     * @param enabled <code>true</code> to enable the control, 
     *   and <code>false</code> to disable it
     * @see #restoreEnableState(Control, Map, String)
     */
    private void saveEnableStateAndSet(Control w, Map h, String key,
            boolean enabled) {
        if (w != null) {
            h.put(key, w.getEnabled() ? Boolean.TRUE : Boolean.FALSE);
            w.setEnabled(enabled);
        }
    }
    /**
     * Captures and returns the enabled/disabled state of the wizard dialog's
     * buttons and the tree of controls for the currently showing page. All
     * these controls are disabled in the process, with the possible exception of
     * the Cancel button.
     *
     * @param keepCancelEnabled <code>true</code> if the Cancel button should