send_custom_email: Fix emailing single users with TOS_VERSION set.

This code path previously threw an exception.

Author: timabbott

zerver/management/commands/send_custom_email.py

@@ -111,7 +111,13 @@ def handle(self, *args: Any, **options: str) -> None:
 
         # Only email users who've agreed to the terms of service.
         if settings.TOS_VERSION is not None:
-            users = users.exclude(tos_version=None)
+            # We need to do a new query because the `get_users` path
+            # passes us a list rather than a QuerySet.
+            users = (
+                UserProfile.objects.select_related()
+                .filter(id__in=[u.id for u in users])
+                .exclude(tos_version=None)
+            )
         send_custom_email(users, options)
 
         if options["dry_run"]: