Skip an external task

System

Hello,

I have a TAG_info that contains an optional e-mail field. If the field is filled in by the user, an external task is executed to send a mail the the specified e-mail address (already implemented) but if the field is left blank, I would like to skip the execution of the external task.

How can this be done (At the moment the external task is always executed, even when the field is blank) ?

Thanks in advance!