fix #640 double email when registered participant is also a follower

rowers/views/racesviews.py

@@ -1873,6 +1873,8 @@ def virtualevent_addboat_view(request, id=0):
             otherrecords = resultobj.objects.filter(
                 race=race).exclude(userid=r.id)
 
+            registereduserids = [otherrecord.userid for otherrecord in otherrecords]
+
             for otherrecord in otherrecords:
                 try:
                     otheruser = Rower.objects.get(id=otherrecord.userid)
@@ -1892,19 +1894,20 @@ def virtualevent_addboat_view(request, id=0):
 
             followers = VirtualRaceFollower.objects.filter(race=race)
 
-            for follower in followers:  # pragma: no cover
+            for follower in followers:  
                 othername = ''
                 if follower.user:
                     othername = follower.user.first_name+' '+follower.user.last_name
 
                 registeredname = r.user.first_name+' '+r.user.last_name
                 email = follower.emailaddress
-                _ = myqueue(
-                    queue,
-                    handle_sendemail_raceregistration,
-                    email, othername,
-                    registeredname, race.name, race.id,
-                )
+                if follower.user.id not in registereduserids:
+                    _ = myqueue(
+                        queue,
+                        handle_sendemail_raceregistration,
+                        email, othername,
+                        registeredname, race.name, race.id,
+                    )
 
             url = reverse('virtualevent_view',
                           kwargs={