Why does updating break my site?

Question

I have a site running Drupal 8.6.10.
I installed it with Composer: composer create-project drupal-composer/drupal-project:8.x-dev JdP8M7b --stability dev --no-interaction
I tried to update it to 8.6.12:

And now, I get an error when I go to any page using my default theme Mayo (no problem when I go to pages using admin theme Seven):

Le site Web a rencontré une erreur inattendue. Veuillez essayer de nouveau plus tard.</br></br><em class="placeholder">Twig\Error\SyntaxError</em>: An exception has been thrown during the compilation of a template ("Attribute "name" does not exist for Node "Twig\Node\CheckToStringNode".") in "themes/contrib/mayo/templates/block--system-menu-block.html.twig". in <em class="placeholder">Twig\Environment->compileSource()</em> (line <em class="placeholder">797</em> of <em class="placeholder">/Users/efalzon/Sites/JdP8M7b/vendor/twig/twig/src/Environment.php</em>). <pre class="backtrace">Drupal\Core\Template\TwigNodeTrans->compileString(Object) (Line: 37)
Drupal\Core\Template\TwigNodeTrans->compile(Object) (Line: 121)
Twig\Node\Node->compile(Object) (Line: 103)
Twig\Compiler->subcompile(Object) (Line: 38)
Twig\Node\BlockNode->compile(Object) (Line: 121)
Twig\Node\Node->compile(Object) (Line: 121)
Twig\Node\Node->compile(Object) (Line: 103)
Twig\Compiler->subcompile(Object) (Line: 108)
Twig\Node\ModuleNode->compileTemplate(Object) (Line: 78)
Twig\Node\ModuleNode->compile(Object) (Line: 92)
Twig\Compiler->compile(Object) (Line: 771)
Twig\Environment->compile(Object) (Line: 792)
Twig\Environment->compileSource(Object) (Line: 482)
Twig\Environment->loadClass('__TwigTemplate_b7128b0551d0a78f96214d3c3a23560aec4c9e673cc8d52ea34b27fddaa41d4c', 'themes/contrib/mayo/templates/block--system-menu-block.html.twig', NULL) (Line: 446)
Twig\Environment->loadTemplate('themes/contrib/mayo/templates/block--system-menu-block.html.twig') (Line: 64)
twig_render_template('themes/contrib/mayo/templates/block--system-menu-block.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('block', Array) (Line: 437)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 450)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 195)
Drupal\Core\Render\Renderer->render(Array) (Line: 490)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 351)
__TwigTemplate_f653a38d19f626722860c776e638e47ff1e967a1bbf99439b558862341cf6bd3->doDisplay(Array, Array) (Line: 427)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 398)
Twig\Template->display(Array) (Line: 406)
Twig\Template->render(Array) (Line: 64)
twig_render_template('themes/contrib/mayo/templates/page.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('page', Array) (Line: 437)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 195)
Drupal\Core\Render\Renderer->render(Array) (Line: 490)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 105)
__TwigTemplate_c0a9c9d745b014e5001be99f83f1adff9ca682260338f6d6a70aefea4539e7eb->doDisplay(Array, Array) (Line: 427)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 398)
Twig\Template->display(Array) (Line: 406)
Twig\Template->render(Array) (Line: 64)
twig_render_template('themes/contrib/mayo/templates/html.html.twig', Array) (Line: 384)
Drupal\Core\Theme\ThemeManager->render('html', Array) (Line: 437)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 195)
Drupal\Core\Render\Renderer->render(Array) (Line: 147)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 582)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 148)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch('kernel.view', Object) (Line: 156)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 52)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 693)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)
</pre>  

Any idea?

Answer 1

As an easy workaround you should try downgrading your twig

composer require twig/twig 1.37.1

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