Fix some documentation return types (#1679)

src/core/PaperScope.js

@@ -311,6 +311,7 @@ var PaperScope = Base.extend(/** @lends PaperScope# */{
              * Retrieves a PaperScope object with the given scope id.
              *
              * @param id
+             * @return {PaperScope}
              */
             get: function(id) {
                 return this._scopes[id] || null;

src/item/Item.js

@@ -2854,7 +2854,7 @@ new function() { // Injection scope for hit-test functions shared with project
      *
      * @param {Boolean} [recursively=false] whether an item with children should be
      * considered empty if all its descendants are empty
-     * @return Boolean
+     * @return {Boolean}
      */
     isEmpty: function(recursively) {
         var children = this._children;