The Session contains the cmsSite (or web site in other words). this value is used as long as the session is alive. When the session expires, the cmssite value doesn't exist anymore, and you should provide it, by following one of the url patterns related to the site you wanna display (which is in your case localhost:9001/acceleratorstorefront/?site=electronics
Please check the CmsSiteFilter, it contains all the code responsible for that behavior.