[modxcms#9859] Prevent conditional output filter recursion

Merge remote-tracking branch 'TriAnMan/bugfix-9859-v2' into bug-9859

* TriAnMan/bugfix-9859-v2:
  [modxcms#9859] Fix a near infinite recursion loop on TV ouptut filtering

core/docs/changelog.txt

@@ -2,6 +2,7 @@
 This file shows the changes in recent releases of MODX. The most current release is usually the
 development release, and is only shown to give an idea of what's currently in the pipeline.
 
+- [#9859] Prevent conditional output filter recursion
 - [#6138] Handle offline errors in RSS feeds
 - Refresh file tree after removing file
 - [#9946] Do not cache modResource::$_isForward

core/model/modx/filters/modoutputfilter.class.php

@@ -49,7 +49,7 @@ function __construct(modX &$modx) {
     /**
      * Filters the output
      * 
-     * @param mixed $element The element to filter
+     * @param modElement $element The element to filter
      */
     public function filter(&$element) {
         $usemb = function_exists('mb_strlen') && (boolean)$this->modx->getOption('use_multibyte',null,false);
@@ -633,6 +633,8 @@ public function filter(&$element) {
                     $this->modx->log(modX::LOG_LEVEL_ERROR,$e->getMessage());
                 }
             }
+            // convert $output to string if there were any processing
+            $output = (string)$output;
         }
     }