title: magento 2 Element 'referenceContainer', attribute 'after': The attribute 'after' is not allowed
body: <p>I'm getting this error in magento 2. I didn't do any updates, this error just suddenly appeared. </p>
  
  <p>I see that I have to remove the "after" attribute, but where can I find where?</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>1 exception(s):
  Exception #0 (Magento\Framework\Config\Dom\ValidationException): Element 'referenceContainer', attribute 'after': The attribute 'after' is not allowed.
  Line: 1251
  
  
  Exception #0 (Magento\Framework\Config\Dom\ValidationException): Element 'referenceContainer', attribute 'after': The attribute 'after' is not allowed.
  Line: 1251
  
  #0 /www/htdocs/domain/vendor/magento/framework/Config/Dom.php(115): Magento\Framework\Config\Dom-&gt;_initDom('&lt;layout xmlns:x...')
  #1 /www/htdocs/domain/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php(111): Magento\Framework\Config\Dom-&gt;__construct('&lt;layout xmlns:x...', Object(Magento\Framework\App\Arguments\ValidationState), Array, NULL, '/www/htdocs/w00...', '%message%\nLine:...')
  #2 /www/htdocs/domain/vendor/magento/framework/ObjectManager/Factory/Dynamic/Developer.php(66): Magento\Framework\ObjectManager\Factory\AbstractFactory-&gt;createObject('Magento\\Framewo...', Array)
  #3 /www/htdocs/domain/vendor/magento/framework/ObjectManager/ObjectManager.php(56): Magento\Framework\ObjectManager\Factory\Dynamic\Developer-&gt;create('Magento\\Framewo...', Array)
  #4 /www/htdocs/domain/vendor/magento/framework/Config/DomFactory.php(42): Magento\Framework\ObjectManager\ObjectManager-&gt;create('Magento\\Framewo...', Array)
  #5 /www/htdocs/domain/vendor/magento/framework/View/Model/Layout/Update/Validator.php(125): Magento\Framework\Config\DomFactory-&gt;createDom(Array)
  #6 /www/htdocs/domain/vendor/magento/framework/View/Model/Layout/Merge.php(461): Magento\Framework\View\Model\Layout\Update\Validator-&gt;isValid('&lt;layout xmlns:x...', 'layout_merged', false)
  #7 /www/htdocs/domain/vendor/magento/framework/View/Model/Layout/Merge.php(442): Magento\Framework\View\Model\Layout\Merge-&gt;_validateMergedLayout('LAYOUT_frontend...', '&lt;body&gt;\n   &lt;refe...')
  #8 /www/htdocs/domain/generated/code/Magento/Framework/View/Model/Layout/Merge/Interceptor.php(193): Magento\Framework\View\Model\Layout\Merge-&gt;load(Array)
  #9 /www/htdocs/domain/vendor/magento/framework/View/Layout/Builder.php(86): Magento\Framework\View\Model\Layout\Merge\Interceptor-&gt;load()
  #10 /www/htdocs/domain/vendor/magento/framework/View/Layout/Builder.php(63): Magento\Framework\View\Layout\Builder-&gt;loadLayoutUpdates()
  #11 /www/htdocs/domain/vendor/magento/framework/View/Layout.php(254): Magento\Framework\View\Layout\Builder-&gt;build()
  #12 /www/htdocs/domain/vendor/magento/framework/View/Layout.php(875): Magento\Framework\View\Layout-&gt;build()
  #13 /www/htdocs/domain/generated/code/Magento/Framework/View/Layout/Interceptor.php(414): Magento\Framework\View\Layout-&gt;getBlock('page_content_he...')
  #14 /www/htdocs/domain/vendor/magento/module-cms/Helper/Page.php(171): Magento\Framework\View\Layout\Interceptor-&gt;getBlock('page_content_he...')
  #15 /www/htdocs/domain/vendor/magento/module-cms/Controller/Noroute/Index.php(44): Magento\Cms\Helper\Page-&gt;prepareResultPage(Object(Magento\Cms\Controller\Noroute\Index\Interceptor), 'no-route')
  #16 /www/htdocs/domain/generated/code/Magento/Cms/Controller/Noroute/Index/Interceptor.php(24): Magento\Cms\Controller\Noroute\Index-&gt;execute()
  #17 /www/htdocs/domain/vendor/magento/framework/App/Action/Action.php(107): Magento\Cms\Controller\Noroute\Index\Interceptor-&gt;execute()
  #18 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Framework\App\Action\Action-&gt;dispatch(Object(Magento\Framework\App\Request\Http))
  #19 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Cms\Controller\Noroute\Index\Interceptor-&gt;___callParent('dispatch', Array)
  #20 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Cms\Controller\Noroute\Index\Interceptor-&gt;Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
  #21 /www/htdocs/domain/generated/code/Magento/Cms/Controller/Noroute/Index/Interceptor.php(39): Magento\Cms\Controller\Noroute\Index\Interceptor-&gt;___callPlugins('dispatch', Array, Array)
  #22 /www/htdocs/domain/vendor/magento/framework/App/FrontController.php(55): Magento\Cms\Controller\Noroute\Index\Interceptor-&gt;dispatch(Object(Magento\Framework\App\Request\Http))
  #23 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Framework\App\FrontController-&gt;dispatch(Object(Magento\Framework\App\Request\Http))
  #24 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Framework\App\FrontController\Interceptor-&gt;___callParent('dispatch', Array)
  #25 /www/htdocs/domain/vendor/magento/module-store/App/FrontController/Plugin/RequestPreprocessor.php(94): Magento\Framework\App\FrontController\Interceptor-&gt;Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
  #26 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(135): Magento\Store\App\FrontController\Plugin\RequestPreprocessor-&gt;aroundDispatch(Object(Magento\Framework\App\FrontController\Interceptor), Object(Closure), Object(Magento\Framework\App\Request\Http))
  #27 /www/htdocs/domain/vendor/mirasvit/module-search-autocomplete/src/SearchAutocomplete/Plugin/ResponsePlugin.php(157): Magento\Framework\App\FrontController\Interceptor-&gt;Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
  #28 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(135): Mirasvit\SearchAutocomplete\Plugin\ResponsePlugin-&gt;aroundDispatch(Object(Magento\Framework\App\FrontController\Interceptor), Object(Closure), Object(Magento\Framework\App\Request\Http))
  #29 /www/htdocs/domain/vendor/magento/module-page-cache/Model/App/FrontController/BuiltinPlugin.php(73): Magento\Framework\App\FrontController\Interceptor-&gt;Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
  #30 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(135): Magento\PageCache\Model\App\FrontController\BuiltinPlugin-&gt;aroundDispatch(Object(Magento\Framework\App\FrontController\Interceptor), Object(Closure), Object(Magento\Framework\App\Request\Http))
  #31 /www/htdocs/domain/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Framework\App\FrontController\Interceptor-&gt;Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))
  #32 /www/htdocs/domain/generated/code/Magento/Framework/App/FrontController/Interceptor.php(26): Magento\Framework\App\FrontController\Interceptor-&gt;___callPlugins('dispatch', Array, Array)
  #33 /www/htdocs/domain/vendor/magento/framework/App/Http.php(135): Magento\Framework\App\FrontController\Interceptor-&gt;dispatch(Object(Magento\Framework\App\Request\Http))
  #34 /www/htdocs/domain/vendor/magento/framework/App/Bootstrap.php(256): Magento\Framework\App\Http-&gt;launch()
  #35 /www/htdocs/domain/index.php(39): Magento\Framework\App\Bootstrap-&gt;run(Object(Magento\Framework\App\Http))
  #36 {main}</code></pre>
  </div>
  </div>
  </p>
  
  <p>I see that I have to remove the "after" attribute, but where can I find where?</p>
  
  <p>thanks</p>