Just set the "default value" in the server behavior to be the current value in the database and then the value won't change when it is left blank since it will use the default.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.