tsv empty column error

[scarlhoff]

Hello!

Forgetting to put NA (or anything) in the BAM column of the tsv file currently results in this unspecific error:

Cannot invoke method matches() on null object -- Check script '/projects1/clusterhomes/carlhoff/.nextflow/assets/nf-core/eager/main.nf' at line: 3424 or see '.nextflow.log' file for more details

row 3424 contains: def bam = row.BAM.matches('NA') ? 'NA' : return_file(row.BAM)

Would be great if the error could be more specific, since it looks more scary than it is.

[jfy133]

I guess 'nothing' isn't considered a string by matches so fails (rather than continue to the downstream file validation step).

Should throw an error if it's nothing.