delete spammers script: fix --id_range command

html/ops/delete_spammers.php

@@ -179,8 +179,11 @@ for ($i=1; $i<$argc; $i++) {
             die ("bad args\n");
         }
         for ($i=$id1; $i <= $id2; $i++) {
-            echo "deleting $i\n";
-            delete_user($i);
+            $user = BoincUser::lookup_id($i);
+            if ($user) {
+                echo "deleting user $i\n";
+                delete_user($user);
+            }
         }
     } else if ($argv[$i] == "--banished") {
         delete_banished();