code: public void setImage(String src) {
          if (src == null) {
              throw new RuntimeException("Cannot set image to null. Call removeImage() if you wanted to remove the image");
          }
  
          if (imageElem == null) {
              imageElem = Document.get().createImageElement();
              // must be first child according to jquery.mobile-1.4.x.css
              if (anchor != null) anchor.insertFirst(imageElem);
              else insertFirstChild(imageElem);
          }
          imageElem.setAttribute("src", src);
          getElement().addClassName(STYLE_UI_LI_HAS_THUMB);
      }
docs: Sets the image on this list item to the given source url.
  <br> Neither 'jqm4gwt-listitem-thumb' nor 'jqm4gwt-listitem-icon' class is added.