New Post: web page title is blank when use PathInfo to show the global data item attached to the Page

Composite C1 4.0
Build 4.0.4897.31550
no custom asp.net sitemap provider code

there is some razor function wirte by myself in this razor template, but i have already remove title tag from all these razor function code.

and i have test that : change the title tag to
<title>1234</title>

the page for the first url above is 1234
and the page for the second url above is blank.
So strange...