org.jahia.taglibs.uicomponents.sitemap.SitemapTag error raises quit frequently after validation the home page

Install the last build , choose corporate demo for creating my first site, try to publish only home page on both FR and EN. and clicked quickly on refesh button of the navigator (f5) maybe before the WF task had been finished and here the exception in my console. Note that this error I have enough frequently when browsing between live and edit mode..

see attachment for the exception