fixed endless error loop in error handler

this happended when `stream` was set on the response but the stream resouce was invalid
either because it was already sent or became invalid for some other cases.

fixes #9046

framework/CHANGELOG.md

@@ -22,6 +22,7 @@ Yii Framework 2 Change Log
 - Bug #8661: Fixed `yii.activeForm.js` scrolling to top (nkovacs)
 - Bug #8772: ActiveQuery failed removing duplicate records after join when the resultset did not contain the pk values e.g. after grouping (cebe)
 - Bug #8900: Fixed determine active menu item with url-alias in route `\yii\widgets\Menu::isItemActive()` (demi)
+- Bug #9046: Fixed problem with endless error loop when an error occurred after sending a stream or file download response to the user (cebe)
 - Bug: Fixed string comparison in `BaseActiveRecord::unlink()` which may result in wrong comparison result for hash valued primary keys starting with `0e` (cebe)
 - Bug: Pass correct action name to `yii\console\Controller::options()` when default action was requested (cebe)
 - Bug: Automatic garbage collection in `yii\caching\FileCache` was not triggered (kidol)

framework/web/ErrorHandler.php

@@ -69,7 +69,12 @@ class ErrorHandler extends \yii\base\ErrorHandler
     {
         if (Yii::$app->has('response')) {
             $response = Yii::$app->getResponse();
+            // reset parameters of response to avoid interference with partially created response data
+            // in case the error occurred while sending the response.
             $response->isSent = false;
+            $response->stream = null;
+            $response->data = null;
+            $response->content = null;
         } else {
             $response = new Response();
         }