If the lead is not in the CRM, it may explain why this is coming empty (And I gather the lead is not is the CRM because the lead owner first name token resolve to its default value).
What is weird is that it should at least display the first and last name.
You would rather use the usual lead tokens such as first name, last name, company name, etc...
I agree Grégoire. I've encountered this before. The standard sync interval with Marketo and Salesforce is 5 minutes. So If you sync to SFDC and sent the alert straight after, it's likely to be empty, as it wasn't synced yet. Try putting an 11 minute delay in the notification. If it's still empty, something else might be the problem.