That is perfectly normal. You upgraded the blog to 1.7, it is not a fresh installation, correct?my blog is running 1.7 (at least it says so), the "URL to blog" field is empty in the admin-interface and in the db I find only baseURL (no defaultBaseURL)
The option "URL to blog" previously was baseURL. Now it is called defaultBaseURL and baseURL is either that option or getting autodetected. My patch will add a task to the upgorader to move baseURL ot defaultBaseURL, if only the first is present.