Don't do a deferred start chat if user is welcome user

There's no point in deferring creating a new DM with the welcome user because the setMxId dialog will do so anyway.

src/components/structures/MatrixChat.js

@@ -721,6 +721,9 @@ module.exports = React.createClass({
         );
         // Use a deferred action to reshow the dialog once the user has registered
         if (MatrixClientPeg.get().isGuest()) {
+            // No point in making 2 DMs with welcome bot. This assumes view_set_mxid will
+            // result in a new DM with the welcome user.
+            if (userId !== this.props.config.welcomeUserId) {
                 dis.dispatch({
                     action: 'do_after_sync_prepared',
                     deferred_action: {
@@ -728,6 +731,7 @@ module.exports = React.createClass({
                         user_id: userId,
                     },
                 });
+            }
             dis.dispatch({
                 action: 'view_set_mxid',
             });