scheduled reminder emails activities recorded when emails not sent

When scheduled reminders go out they create activities saying an email was sent. If the person has no email address the action_log records this but an activity is still created.

2 options
1) simply block the activity (we are going to implement this as a 1 line fix for now in our repo)

2) create an activity indicating that an email WOULD have been sent had it been possible. I think this would be useful for administrators to organise their follow ups around - e.g search for these activities & send letters