Do not allow user leave the room ONLY if it is a livechat room

Closes #3121

packages/rocketchat-livechat/server/startup.js

@@ -21,7 +21,10 @@ Meteor.startup(() => {
 		return room.t === 'l' && RocketChat.authz.hasPermission(user._id, 'view-livechat-rooms');
 	});
 
-	RocketChat.callbacks.add('beforeLeaveRoom', function(user) {
+	RocketChat.callbacks.add('beforeLeaveRoom', function(user, room) {
+		if (room.t !== 'l') {
+			return user;
+		}
 		throw new Meteor.Error(TAPi18n.__('You_cant_leave_a_livechat_room_Please_use_the_close_button', {
 			lng: user.language || RocketChat.settings.get('language') || 'en'
 		}));