you can skip adding empty dev file and infer time is reduced

[Akshaysharma29]

Hi team, I have added a check so creating an empty dev file can be skipped in colab and this will reduce infer time as well.
Thanks.

[eisenjulian]

Thanks for the proposed changes, it's a great idea to make inference faster when no test set is needed. To make it not fail silently in the case of missing data, we would prefer if we added an explicit boolean flag to the executable, something like skip_test_set so we can use that in the loops over TestSet to skip the evaluation.