[Slack] Fix unread issue when channel content is no longer available

srv/src/slackData.js

@@ -89,6 +89,8 @@ SlackChan.prototype.update = function(chanData, ctx, t, idPrefix) {
         else
             chanData["last_msg"] = chanData["last_read"];
     }
+    if (chanData["last_msg"] !== undefined && chanData["last_read"] !== undefined && chanData["last_msg"] < chanData["last_read"])
+        chanData["last_read"] = chanData["last_msg"];
     return Room.prototype.update.call(this, chanData, ctx, t, idPrefix);
 };
 
@@ -124,6 +126,8 @@ SlackIms.prototype.update = function(chanData, ctx, t, idPrefix) {
         else
             chanData["last_msg"] = chanData["last_read"];
     }
+    if (chanData["last_msg"] !== undefined && chanData["last_read"] !== undefined && chanData["last_msg"] < chanData["last_read"])
+        chanData["last_read"] = chanData["last_msg"];
     return PrivateMessageRoom.prototype.update.call(this, chanData, ctx, t, idPrefix);
 };