MSMARCO minidev.qrels empty?

[seanmacavaney]

Reported by @HangCui0510 in Georgetown-IR-Lab/covid-neural-ir#3.

[seanmacavaney]

Should be being built right here: https://github.com/Georgetown-IR-Lab/OpenNIR/blob/master/onir/datasets/msmarco.py#L237

Nothing obvious looks wrong. It's especially strange because the query file was built properly, and it's doing essentially the same thing: https://github.com/Georgetown-IR-Lab/OpenNIR/blob/master/onir/datasets/msmarco.py#L210