Merge pull request #3727 from K900/patch-1

Fix #3624

(cherry picked from commit 06db5f8bca)
Signed-off-by: Joshua M. Boniface <joshua@boniface.me>

Jellyfin.Server.Implementations/Users/UserManager.cs

@@ -592,18 +592,13 @@ namespace Jellyfin.Server.Implementations.Users
             }
 
             var defaultName = Environment.UserName;
-            if (string.IsNullOrWhiteSpace(defaultName))
+            if (string.IsNullOrWhiteSpace(defaultName) || !IsValidUsername(defaultName))
             {
                 defaultName = "MyJellyfinUser";
             }
 
             _logger.LogWarning("No users, creating one with username {UserName}", defaultName);
 
-            if (!IsValidUsername(defaultName))
-            {
-                throw new ArgumentException("Provided username is not valid!", defaultName);
-            }
-
             var newUser = CreateUser(defaultName);
             newUser.SetPermission(PermissionKind.IsAdministrator, true);
             newUser.SetPermission(PermissionKind.EnableContentDeletion, true);