Fix bug

[FilippoOlivo]

No description provided.

[dario-coscia]

why = as well?

[FilippoOlivo]

why = as well?

Essentially, this handles the case when there is a single input point in the condition. Indeed, if we have, for example, only one point in the dataset, the loop behaves as follows:
• Train: offset == 0, then increment by 1 (offset == len_condition). In this case, we add the point.
• Test: offset == 1, we enter the if condition and decrement. However, in this case, we do not add any points.
• Validation: offset == 0 (similar to the train case).

with the new condition in test_split a datapoint is added, since the offset is reset to 0 after train_split creation

[FilippoOlivo]

@dario-coscia If ok, I merge this small fix