fix: dont update title on client with falsy value except empty string

Author: pimlie

src/client/updaters/title.js

@@ -4,7 +4,7 @@
  * @param  {String} title - the new title of the document
  */
 export default function updateTitle (title) {
-  if (title === undefined) {
+  if (!title && title !== '') {
     return
   }