document was mistakenly a reference to the env.js document that has n…

…ow been removed

lib/couchdb/design_document.js

@@ -78,7 +78,7 @@ function DesignDocument(fn){
     }
 
     this.toDocument = function(){
-        if (document._id == undefined) throw new Error("Id must be specified before toDocument is valid");
+        if (this.document._id == undefined) throw new Error("Id must be specified before toDocument is valid");
 
         return this.document;
     };