Fix HTML helper method should set up in handle_page()

sphinx/builders/html.py

@@ -353,7 +353,6 @@ class StandaloneHTMLBuilder(Builder):
             parents = [],
             logo = logo,
             favicon = favicon,
-            warn = self.warn
         )
         if self.theme:
             self.globalcontext.update(
@@ -774,6 +773,7 @@ class StandaloneHTMLBuilder(Builder):
     def handle_page(self, pagename, addctx, templatename='page.html',
                     outfilename=None, event_arg=None):
         ctx = self.globalcontext.copy()
+        ctx['warn'] = self.warn
         # current_page_name is backwards compatibility
         ctx['pagename'] = ctx['current_page_name'] = pagename
         default_baseuri = self.get_target_uri(pagename)