issue creation by mail - Imap: Created account email has "This action was initiated by null (null)."

to reproduce:

1. configure jira to create issues by mail using imap
2. send an imail to that email account to create a new issue (with createuser parameter = true) from an email address that is not registered on JIRA

I think that we need to change this text to any mo accurate. null is not the correct one