Why i can't to apply Sencha Grid with UiBinder and Eclipse "Design" tab ? Any else - Viewportm BorderLayouts, ContentPanels, Fields works fine but Grid (created by @UiFactory method) took me below crash:

java.lang.AssertionError: This UIObject's element is not set; you may be missing a call to either Composite.initWidget() or UIObject.setElement() at com.google.gwt.user.client.ui.UIObject.getElement(UIObject.java:527) at com.sencha.gxt.widget.core.client.Component.getElement(Component.java:327) at com.sencha.gxt.widget.core.client.Component.getElement(Component.java:1) at com.sencha.gxt.widget.core.client.container.Container.doPhysicalAttach(Container.java:319) at com.sencha.gxt.widget.core.client.container.Container.insert(Container.java:393) at com.sencha.gxt.widget.core.client.container.SimpleContainer.setWidget(SimpleContainer.java:109) at com.sencha.gxt.widget.core.client.container.SimpleContainer.add(SimpleContainer.java:56)
What is wonder of Grid ? My code as a whole forks fine under development and normal mode, but crash into "Design" Eclipse tab.