Very simple rule execution for when a "sub-task" is created; if the Assignee is blank, then assign to the Reporter:

However every time this action occurs, Jira will send out email notifications because 'Jira Automation' is assigning the ticket, so it's not considered a self-action (whereby email notifications don't get sent). Shown here:

Is there a way round to stop this from happening?
In other words this should be a 'silent' event because the reporter triggers the rule, and so does not need to be notified.
P.S. obviously our users don't want to turn OFF 'get email activity if Assigned an issue' from Jira Personal Settings, as this is needed is an actual user changes the Assignee.