Redirecting to user

current user == 0 Redirecting to user Redirecting to user. The website encountered an unexpected error. Please try again later.
RuntimeException: Failed to start the session because headers have already been sent by "/home/d10seguranet/public_html/web/modules/custom/seguranet_activity/src/Controller/ActivityController.php" at line 700. in Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (line 132 of /home/d10seguranet/public_html/vendor/symfony/http-foundation/Session/Storage/NativeSessionStorage.php).

Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage->start() (Line: 144)
Drupal\Core\Session\SessionManager->startNow() (Line: 175)
Drupal\Core\Session\SessionManager->save() (Line: 159)
Symfony\Component\HttpFoundation\Session\Session->save() (Line: 61)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 191)
Drupal\page_cache\StackMiddleware\PageCache->fetch(Object, 1, 1) (Line: 128)
Drupal\page_cache\StackMiddleware\PageCache->lookup(Object, 1, 1) (Line: 82)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 686)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)