removed @channel (#3497)

webapp/components/channel_header.jsx

@@ -128,10 +128,14 @@ export default class ChannelHeader extends React.Component {
         if (user.notify_props && user.notify_props.mention_keys) {
             const termKeys = UserStore.getMentionKeys(user.id);
 
-            if (user.notify_props.channel === 'true' && termKeys.indexOf('@channel') !== -1 && termKeys.indexOf('@all') !== -1) {
-                termKeys.splice(termKeys.indexOf('@channel'), 1);
-                termKeys.splice(termKeys.indexOf('@all'), 1);
+            if (termKeys.indexOf('@channel') !== -1) {
+                termKeys[termKeys.indexOf('@channel')] = '';
             }
+
+            if (termKeys.indexOf('@all') !== -1) {
+                termKeys[termKeys.indexOf('@all')] = '';
+            }
+
             terms = termKeys.join(' ');
         }