Minor fix

backend/filedelete.php

@@ -36,7 +36,7 @@ if (isset($postData) && !empty($postData)) {
       mysqli_query($mysqli,$sql);
       $msg = "file successfully deleted";
       echo json_encode($msg);
-      if (file_exists($exec_path)){
+      if (file_exists($exec_path) && is_file($exec_path)) {
         unlink($exec_path);
       }
     }