web: fix refered object extractions when page is in context of web site

Base_extractReferredObjectDictFromHtml except that base url to have a
leading /, because we ignore the first character of the normalized URL
returned by Base_normalizeUrlPathname.

By using / as base URL when we are in the context of the website, the
paths passed to Base_normalizeUrlPathname always start by / so we can
safely drop / from the normalized path returned by
Base_normalizeUrlPathname

bt5/erp5_web/SkinTemplateItem/portal_skins/erp5_web/Base_extractReferredObjectDictFromHtml.py

@@ -122,7 +122,7 @@ else:
   root_url = base_url_root_object.absolute_url()
   base_url = base_url_object.absolute_url()
 
-base_path = "."
+base_path = "/"
 if base_url_object.getRelativeUrl().startswith(base_url_root_object.getRelativeUrl()):
   base_path = base_url_object.getRelativeUrl()[len(base_url_root_object.getRelativeUrl()):]
   if base_path and not base_path.startswith("/"):