Handle the case when the stored password is null, but the user tried to login with a password.

Emby.Server.Implementations/Library/DefaultAuthenticationProvider.cs

@@ -61,6 +61,9 @@ namespace Emby.Server.Implementations.Library
                 });
             }
 
+            // Handle the case when the stored password is null, but the user tried to login with a password
+            if (resolvedUser.Password != null)
+            {
                 byte[] passwordbytes = Encoding.UTF8.GetBytes(password);
 
                 PasswordHash readyHash = PasswordHash.Parse(resolvedUser.Password);
@@ -81,6 +84,7 @@ namespace Emby.Server.Implementations.Library
                 {
                     throw new AuthenticationException($"Requested crypto method not available in provider: {readyHash.Id}");
                 }
+            }
 
             if (!success)
             {