Search button is not working.

here is the error message:
Error: Call to undefined function element_set_attributes() in busy_fieldset() (line 74 of C:\xampp\htdocs\Drupal4Contribution\web\themes\busy\busy.theme)
#0 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Theme\ThemeManager.php(317): busy_fieldset(Array)
#1 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\Renderer.php(487): Drupal\Core\Theme\ThemeManager->render('fieldset', Array)
#2 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\Renderer.php(444): Drupal\Core\Render\Renderer->doRender(Array)
#3 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\Renderer.php(444): Drupal\Core\Render\Renderer->doRender(Array)
#4 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\Renderer.php(444): Drupal\Core\Render\Renderer->doRender(Array)
#5 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\Renderer.php(200): Drupal\Core\Render\Renderer->doRender(Array, false)
#6 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\MainContent\HtmlRenderer.php(226): Drupal\Core\Render\Renderer->render(Array, false)
#7 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\Renderer.php(573): Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}()
#8 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\MainContent\HtmlRenderer.php(227): Drupal\Core\Render\Renderer->executeInRenderContext(Object(Drupal\Core\Render\RenderContext), Object(Closure))
#9 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\Render\MainContent\HtmlRenderer.php(117): Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\CurrentRouteMatch))
#10 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\EventSubscriber\MainContentViewSubscriber.php(90): Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object(Symfony\Component\HttpFoundation\Request), Object(Drupal\Core\Routing\CurrentRouteMatch))
#11 C:\xampp\htdocs\Drupal4Contribution\vendor\symfony\event-dispatcher\LegacyEventDispatcherProxy.php(78): Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object(Symfony\Component\HttpKernel\Event\ViewEvent), 'kernel.view', Object(Symfony\Component\EventDispatcher\LegacyEventDispatcherProxy))
#12 C:\xampp\htdocs\Drupal4Contribution\vendor\symfony\http-kernel\HttpKernel.php(163): Symfony\Component\EventDispatcher\LegacyEventDispatcherProxy->dispatch(Object(Symfony\Component\HttpKernel\Event\ViewEvent), 'kernel.view')
#13 C:\xampp\htdocs\Drupal4Contribution\vendor\symfony\http-kernel\HttpKernel.php(80): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#14 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\StackMiddleware\Session.php(57): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#15 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\StackMiddleware\KernelPreHandle.php(47): Drupal\Core\StackMiddleware\Session->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#16 C:\xampp\htdocs\Drupal4Contribution\web\core\modules\page_cache\src\StackMiddleware\PageCache.php(106): Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#17 C:\xampp\htdocs\Drupal4Contribution\web\core\modules\page_cache\src\StackMiddleware\PageCache.php(85): Drupal\page_cache\StackMiddleware\PageCache->pass(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#18 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\StackMiddleware\ReverseProxyMiddleware.php(47): Drupal\page_cache\StackMiddleware\PageCache->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#19 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\StackMiddleware\NegotiationMiddleware.php(52): Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#20 C:\xampp\htdocs\Drupal4Contribution\vendor\stack\builder\src\Stack\StackedHttpKernel.php(23): Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#21 C:\xampp\htdocs\Drupal4Contribution\web\core\lib\Drupal\Core\DrupalKernel.php(705): Stack\StackedHttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#22 C:\xampp\htdocs\Drupal4Contribution\web\index.php(19): Drupal\Core\DrupalKernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#23 {main}