diff --git a/3rdparty/kcfinder/core/class/uploader.php b/3rdparty/kcfinder/core/class/uploader.php
index 447d0ff79..884c58f72 100644
--- a/3rdparty/kcfinder/core/class/uploader.php
+++ b/3rdparty/kcfinder/core/class/uploader.php
@@ -696,7 +696,8 @@ protected function backMsg($message, array $data=null) {
     protected function callBack($url, $message="") {
         $message = text::jsValue($message);
 
-        if ((get_class($this) == "kcfinder\\browser") && ($this->action != "browser"))
+        if ((get_class($this) == "kcfinder\\browser")
+            && ($this->action !== null) && ($this->action != "browser"))
             return;
 
         if (isset($this->opener['name'])) {