Training the test group selection model failed due to a division by zero error

[suhaibmujahid]

https://community-tc.services.mozilla.com/tasks/BDt8JybuSBSNkkIeabJ8Kw/runs/1/logs/public/logs/live.log:

Traceback (most recent call last):
  File "/usr/local/bin/bugbug-train", line 8, in <module>
    sys.exit(main())
             ^^^^^^
  File "/usr/local/lib/python3.12/site-packages/scripts/trainer.py", line 141, in main
    retriever.go(args)
  File "/usr/local/lib/python3.12/site-packages/scripts/trainer.py", line 41, in go
    metrics = model_obj.train(limit=args.limit)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/site-packages/bugbug/model.py", line 574, in train
    self.evaluation()
  File "/usr/local/lib/python3.12/site-packages/bugbug/models/testselect.py", line 865, in evaluation
    do_eval(executor, confidence_threshold, reduction, cap, minimum)
  File "/usr/local/lib/python3.12/site-packages/bugbug/models/testselect.py", line 831, in do_eval
    100
ZeroDivisionError: division by zero