Issue #3332885 - Add validation by user

src/LogMessage.php

@@ -233,7 +233,13 @@ class LogMessage {
    */
   public function getUser(): UserInterface {
     if (!isset($this->user)) {
-      $this->user = User::load($this->context['uid']);
+      if (isset($this->context['uid']) && $user = User::load($this->context['uid'])) {
+        /** @var \Drupal\user\UserInterface user */
+        $this->user = $user;
+      }
+      else {
+        $this->user = User::load(\Drupal::currentUser()->id());
+      }
     }
     return $this->user;
   }