small fix

app/views/admin/tickets/show.html.erb

@@ -351,7 +351,7 @@ $(document).ready(function(){
   $("body").on("click", ".ticket-response-content img, .ticket-query img", function(){
     var el = $(this);
     if(el.parent().prop("tagName") != "A"){
-      if(openImageWindow == null){
+      if(openImageWindow == null || openImageWindow.closed){
         openImageWindow = window.open(el.attr("src"));
       }else{
         openImageWindow.location = el.attr("src");