Typo.

local/modules/Tinymce/Resources/js/tinymce/filemanager/config/config.php

@@ -52,8 +52,6 @@ if (empty($base_url)) {
     $base_url = $request->getSchemeAndHttpHost() . preg_replace('!/tinymce/filemanager/dialog.php.*$!', '', $_SERVER['REQUEST_URI']);
 }
 
-echo "b=$base_url";
-
 // path from base_url to base of upload folder (with start and final /)
 $upload_dir = '/media/upload/';