unhandled error: when participant_id column has missing values, bagel pheno crashes

[surchs]

If the input pheno.tsv file has missing values / empty strings / nan in one of the participant_id columns, things break in unexpected and unhandled ways.

Something like this:	participant_id	other_val	some_val
sub-01	3	10
	4	11
sub-03	5	6

This shouldn't happen if we're handling a regular BIDS participants.tsv file, but it probably does happen. And it will certainly happen once we handle multiple participant_id columns, not all of which will be having values.

We have to decide what to do about this, because at the moment we are iterating over the unique elements in the participant_id column, and nan would be one of these.

My view is that we should have some warnings for missing values in any column as part of a phenotypic validation step (see also #90), and then we should raise some exception if the participant column has a missing value / nan.

While we're at it, we might as well just do this for session ids as well. So tasks are:

• [ ] raise on missing values in participant_id labeled columns
• [ ] raise on missing values in session_id labeled columns
• [ ] provide examples and tests for this

[github-actions[bot]]

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