Call to a member function getTag() on null

Error:
Call to a member function getTag() on null

  at /homepages/33/d342611656/htdocs/joomla4/libraries/src/WebAsset/AssetItem/LangActiveAssetItem.php:48
  at Joomla\CMS\WebAsset\AssetItem\LangActiveAssetItem->__construct()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/WebAsset/WebAssetRegistry.php:247)
  at Joomla\CMS\WebAsset\WebAssetRegistry->createAsset()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/WebAsset/WebAssetRegistry.php:419)
  at Joomla\CMS\WebAsset\WebAssetRegistry->parseRegistryFile()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/WebAsset/WebAssetRegistry.php:351)
  at Joomla\CMS\WebAsset\WebAssetRegistry->parseRegistryFiles()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/WebAsset/WebAssetRegistry.php:159)
  at Joomla\CMS\WebAsset\WebAssetRegistry->add()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/WebAsset/WebAssetManager.php:508)
  at Joomla\CMS\WebAsset\WebAssetManager->registerAsset()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/WebAsset/WebAssetManager.php:234)
  at Joomla\CMS\WebAsset\WebAssetManager->__call()
     (/homepages/33/d342611656/htdocs/joomla4/templates/cassiopeia/error.php:40)
  at require('/homepages/33/d342611656/htdocs/joomla4/templates/cassiopeia/error.php')
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Document/HtmlDocument.php:721)
  at Joomla\CMS\Document\HtmlDocument->_loadTemplate()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Document/HtmlDocument.php:776)
  at Joomla\CMS\Document\HtmlDocument->_fetchTemplate()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Document/HtmlDocument.php:612)
  at Joomla\CMS\Document\HtmlDocument->parse()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Document/HtmlDocument.php:630)
  at Joomla\CMS\Document\HtmlDocument->render()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Document/ErrorDocument.php:139)
  at Joomla\CMS\Document\ErrorDocument->render()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Error/Renderer/HtmlRenderer.php:70)
  at Joomla\CMS\Error\Renderer\HtmlRenderer->render()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Exception/ExceptionHandler.php:126)
  at Joomla\CMS\Exception\ExceptionHandler::render()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Exception/ExceptionHandler.php:72)
  at Joomla\CMS\Exception\ExceptionHandler::handleException()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Application/CMSApplication.php:322)
  at Joomla\CMS\Application\CMSApplication->execute()
     (/homepages/33/d342611656/htdocs/joomla4/includes/app.php:61)
  at require_once('/homepages/33/d342611656/htdocs/joomla4/includes/app.php')
     (/homepages/33/d342611656/htdocs/joomla4/index.php:103)                

RuntimeException:
Failed to start the session because headers have already been sent by "/homepages/33/d342611656/htdocs/joomla4/index.php" at line 1.

  at /homepages/33/d342611656/htdocs/joomla4/libraries/vendor/joomla/session/src/Storage/NativeStorage.php:473
  at Joomla\Session\Storage\NativeStorage->start()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Session/Storage/JoomlaStorage.php:295)
  at Joomla\CMS\Session\Storage\JoomlaStorage->start()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/vendor/joomla/session/src/Session.php:406)
  at Joomla\Session\Session->start()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/vendor/joomla/session/src/Session.php:333)
  at Joomla\Session\Session->has()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Session/Session.php:194)
  at Joomla\CMS\Session\Session->get()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Factory.php:372)
  at Joomla\CMS\Factory::getUser()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Application/SiteApplication.php:562)
  at Joomla\CMS\Application\SiteApplication->initialiseApp()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Application/SiteApplication.php:226)
  at Joomla\CMS\Application\SiteApplication->doExecute()
     (/homepages/33/d342611656/htdocs/joomla4/libraries/src/Application/CMSApplication.php:293)
  at Joomla\CMS\Application\CMSApplication->execute()
     (/homepages/33/d342611656/htdocs/joomla4/includes/app.php:61)
  at require_once('/homepages/33/d342611656/htdocs/joomla4/includes/app.php')
     (/homepages/33/d342611656/htdocs/joomla4/index.php:103)