Fixing case with only time features and yearly freq

[dcmaddix]

• Fixed MQ-CNN with yearly freq and only time as the dynamic feature
• In this case no dynamic features are created because the time feature is empty for Y freq and dynamic_feat is None
• Updated to create the dummy zero feature in this case
• Added test_mqcnn_covariate_smoke_test to use freq = Y to test this. Before would fail with add_time_feature = True, add_age_feature = False and use_feat_dyanmic_real = True

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.