Call to a member function getTag() on null

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

  at /homepages/1/d406040521/htdocs/boispaille/libraries/src/WebAsset/AssetItem/LangActiveAssetItem.php:46
  at Joomla\CMS\WebAsset\AssetItem\LangActiveAssetItem->__construct()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/WebAsset/WebAssetRegistry.php:241)
  at Joomla\CMS\WebAsset\WebAssetRegistry->createAsset()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/WebAsset/WebAssetRegistry.php:424)
  at Joomla\CMS\WebAsset\WebAssetRegistry->parseRegistryFile()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/WebAsset/WebAssetRegistry.php:347)
  at Joomla\CMS\WebAsset\WebAssetRegistry->parseRegistryFiles()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/WebAsset/WebAssetRegistry.php:128)
  at Joomla\CMS\WebAsset\WebAssetRegistry->get()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/WebAsset/WebAssetManager.php:277)
  at Joomla\CMS\WebAsset\WebAssetManager->useAsset()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/WebAsset/WebAssetManager.php:245)
  at Joomla\CMS\WebAsset\WebAssetManager->__call()
     (/homepages/1/d406040521/htdocs/boispaille/templates/cassiopeia/error.php:38)
  at require('/homepages/1/d406040521/htdocs/boispaille/templates/cassiopeia/error.php')
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Document/HtmlDocument.php:779)
  at Joomla\CMS\Document\HtmlDocument->_loadTemplate()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Document/HtmlDocument.php:838)
  at Joomla\CMS\Document\HtmlDocument->_fetchTemplate()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Document/HtmlDocument.php:641)
  at Joomla\CMS\Document\HtmlDocument->parse()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Document/HtmlDocument.php:660)
  at Joomla\CMS\Document\HtmlDocument->render()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Document/ErrorDocument.php:140)
  at Joomla\CMS\Document\ErrorDocument->render()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Error/Renderer/HtmlRenderer.php:69)
  at Joomla\CMS\Error\Renderer\HtmlRenderer->render()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Exception/ExceptionHandler.php:131)
  at Joomla\CMS\Exception\ExceptionHandler::render()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Exception/ExceptionHandler.php:74)
  at Joomla\CMS\Exception\ExceptionHandler::handleException()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Application/CMSApplication.php:311)
  at Joomla\CMS\Application\CMSApplication->execute()
     (/homepages/1/d406040521/htdocs/boispaille/includes/app.php:63)
  at require_once('/homepages/1/d406040521/htdocs/boispaille/includes/app.php')
     (/homepages/1/d406040521/htdocs/boispaille/index.php:35)                

RuntimeException:
Failed to start the session because headers have already been sent by "/homepages/1/d406040521/htdocs/boispaille/index.php" at line 1.

  at /homepages/1/d406040521/htdocs/boispaille/libraries/vendor/joomla/session/src/Storage/NativeStorage.php:473
  at Joomla\Session\Storage\NativeStorage->start()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Session/Storage/JoomlaStorage.php:305)
  at Joomla\CMS\Session\Storage\JoomlaStorage->start()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/vendor/joomla/session/src/Session.php:406)
  at Joomla\Session\Session->start()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/vendor/joomla/session/src/Session.php:333)
  at Joomla\Session\Session->has()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Session/Session.php:198)
  at Joomla\CMS\Session\Session->get()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Factory.php:338)
  at Joomla\CMS\Factory::getUser()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Application/SiteApplication.php:619)
  at Joomla\CMS\Application\SiteApplication->initialiseApp()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Application/SiteApplication.php:222)
  at Joomla\CMS\Application\SiteApplication->doExecute()
     (/homepages/1/d406040521/htdocs/boispaille/libraries/src/Application/CMSApplication.php:278)
  at Joomla\CMS\Application\CMSApplication->execute()
     (/homepages/1/d406040521/htdocs/boispaille/includes/app.php:63)
  at require_once('/homepages/1/d406040521/htdocs/boispaille/includes/app.php')
     (/homepages/1/d406040521/htdocs/boispaille/index.php:35)