Store chat messages in sessionStorage

so that they're cleared when the last tab closes

src/headless/converse-chatboxes.js

@@ -293,7 +293,7 @@ converse.plugins.add('converse-chatboxes', {
             initMessages () {
                 this.messages = new _converse.Messages();
                 const storage = _converse.config.get('storage');
-                this.messages.browserStorage = new Backbone.BrowserStorage[storage](
+                this.messages.browserStorage = new Backbone.BrowserStorage.session(
                     `converse.messages-${this.get('jid')}-${_converse.bare_jid}`);
                 this.messages.chatbox = this;
 

src/headless/converse-muc.js

@@ -1485,7 +1485,7 @@ converse.plugins.add('converse-muc', {
              * disconnected, so that they will be properly entered again
              * when fetched from session storage.
              */
-            _converse.chatboxes.each(function (model) {
+            _converse.chatboxes.each(model => {
                 if (model.get('type') === _converse.CHATROOMS_TYPE) {
                     model.save('connection_status', converse.ROOMSTATUS.DISCONNECTED);
                 }