Typo3 Script: Text content of current page
===

I am trying to generate the go:description-tag, which is needed by Facebook, dynamically out of the content of the shown page. My idea is to use the content-text of the page if there is no meta description given. I tried this script:

    page.headerData.838 = CONTENT
    page.headerData.838 {
      table=tt_content
      select {
        where = (CType = "text")
      }
      renderObj=TEXT
      renderObj{
        field=bodytext
        stdWrap.stripHtml=1
        noTrimWrap =|<meta property="og:description" content="|" />| 
      }
    } 

The problem is that this tag not even appears on the page. So what's the catch?