AssertionError occurs when Enhance.fontFamilyBox() is called on a text input element

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Here's my code (from a widget that extends Composite):

@Override
    protected void onLoad() {
        // Wait until elements are attached to DOM to enhance them.
        fontFamilyTextBox.getElement().setId(GQueryHelper.getUniqueIdForElement());
        $("#" + fontFamilyTextBox.getElement().getId()).as(Enhance).fontFamilyBox();
    }

At runtime, this results in the following exception:

Caused by: java.lang.AssertionError: A widget that has an existing parent 
widget may not be added to the detach list    
 at com.google.gwt.user.client.ui.RootPanel.detachOnWindowClose(RootPanel.java:136)  
 at com.google.gwt.user.client.ui.TextBox.wrap(TextBox.java:69)  
 at gwtquery.plugins.enhance.client.fontpicker.FontPickerFactory.create(FontPickerFactory.java:32)   
 at gwtquery.plugins.enhance.client.fontpicker.FontPickerFactory.create(FontPickerFactory.java:1)    
 at com.google.gwt.query.client.plugins.Widgets.widget(Widgets.java:96)  
 at com.google.gwt.query.client.plugins.Widgets.widgets(Widgets.java:74)     
 at gwtquery.plugins.enhance.client.Enhance.fontFamilyBox(Enhance.java:104)  
 at gwtquery.plugins.enhance.client.Enhance.fontFamilyBox(Enhance.java:100)  
 at com.acme.widget.MainThemePropertyEditor.onLoad(MainThemePropertyEditor.java:114)     
 at com.google.gwt.user.client.ui.Composite.onAttach(Composite.java:171)

Original issue reported on code.google.com by ian.spri...@gmail.com on 26 Apr 2013 at 12:52