make subscriber count work with older server

src/views/messages-view.jsx

@@ -1684,7 +1684,9 @@ class MessagesView extends React.Component {
 
         let lastSeen = null;
         if (isChannel) {
+          if (topic.subcnt) {
             lastSeen = formatMessage(messages.subscriber_count, {count: topic.subcnt});
+          }
         } else {
           const cont = this.props.tinode.getMeTopic().getContact(this.state.topic);
           if (cont) {
@@ -1697,10 +1699,12 @@ class MessagesView extends React.Component {
                 // TODO: also handle user agent in c.seen.ua
               }
             } else if (Tinode.isGroupTopicName(cont.topic)) {
+              if (topic.subcnt) {
                 lastSeen = formatMessage(messages.member_count, {count: topic.subcnt});
               }
             }
           }
+        }
         const avatar = this.state.avatar || true;
         const online = this.state.deleted || topic.isSelfType() ? null :
           this.props.online ? 'online' + (this.state.typingIndicator ? ' typing' : '') : 'offline';

umd/index.dev.js

@@ -11133,9 +11133,11 @@ class MessagesView extends (react__WEBPACK_IMPORTED_MODULE_0___default().Compone
         });
         let lastSeen = null;
         if (isChannel) {
+          if (topic.subcnt) {
             lastSeen = formatMessage(messages.subscriber_count, {
               count: topic.subcnt
             });
+          }
         } else {
           const cont = this.props.tinode.getMeTopic().getContact(this.state.topic);
           if (cont) {
@@ -11148,12 +11150,14 @@ class MessagesView extends (react__WEBPACK_IMPORTED_MODULE_0___default().Compone
                 });
               }
             } else if (tinode_sdk__WEBPACK_IMPORTED_MODULE_2__.Tinode.isGroupTopicName(cont.topic)) {
+              if (topic.subcnt) {
                 lastSeen = formatMessage(messages.member_count, {
                   count: topic.subcnt
                 });
               }
             }
           }
+        }
         const avatar = this.state.avatar || true;
         const online = this.state.deleted || topic.isSelfType() ? null : this.props.online ? 'online' + (this.state.typingIndicator ? ' typing' : '') : 'offline';
         const titleClass = 'panel-title' + (this.state.deleted ? ' deleted' : '');