libs/web: don't send Status: 500 in error500() if header is already sent

modules/admin-core: include template header only once

libs/web/luasrc/dispatcher.lua

@@ -74,13 +74,15 @@ end
 -- @param message	Custom error message (optional)#
 -- @return			false
 function error500(message)
+	if not context.template_header_sent then
 		luci.http.status(500, "Internal Server Error")
-
+	else
 		require("luci.template")
 		if not luci.util.copcall(luci.template.render, "error500", {message=message}) then
 			luci.http.prepare_content("text/plain")
 			luci.http.write(message)
 		end
+	end
 	return false
 end
 

modules/admin-core/luasrc/view/header.htm

@@ -12,4 +12,10 @@ You may obtain a copy of the License at
 $Id$
 
 -%>
-<% include("themes/" .. theme .. "/header") %>
+
+<%
+	if not luci.dispatcher.context.template_header_sent then
+		include("themes/" .. theme .. "/header")
+		luci.dispatcher.context.template_header_sent = true
+	end
+%>