Bugfix. Message indicator wasn't shown

when we received a message for a yet non-existing chat in singleton
mode.

dist/converse.js

@@ -76550,6 +76550,7 @@ var __WEBPACK_AMD_DEFINE_FACTORY__, __WEBPACK_AMD_DEFINE_ARRAY__, __WEBPACK_AMD_
       ChatBoxView: {
         shouldShowOnTextMessage() {
           if (_.includes(['mobile', 'fullscreen', 'embedded'], this.__super__._converse.view_mode)) {
+            this.model.set('hidden', true);
             return false;
           } else {
             return this.__super__.shouldShowOnTextMessage.apply(this, arguments);

src/converse-singleton.js

@@ -66,6 +66,7 @@
             ChatBoxView: {
                 shouldShowOnTextMessage () {
                     if (_.includes(['mobile', 'fullscreen', 'embedded'], this.__super__._converse.view_mode)) {
+                        this.model.set('hidden', true);
                         return false;
                     } else { 
                         return this.__super__.shouldShowOnTextMessage.apply(this, arguments);