In case when the dispatch URL is a named resource server or named renderer, a exception is incorrectly thrown and logged by GenericHstComponent#doBeforeServeResource

For example, when the hst:template contains something like:

+ datetime (hst:template)

• hst:isnamed = true
• hst:renderpath = DateTimeServlet

Then, although in HstComponentInvokerImpl#invokeServeResource correctly dispatch to, say a servlet, is done, but during invokeBeforeServeResource an exception is logged that the resourceID did not end with .jsp or .ftl

This is due to that in the case of the hst:template above, the resourceId is empty Strig instead of null

Reproduce for testers:

Start up the testsuite and visit the homepage
Wait one minute : After one minute, a warning is logged (every minute a ajax resource call is done)

Verify if fixed for testers: The above warning should not happen any more