Duplicated fishing_event_ids with join_sample_ids = TRUE

[ecophilina]

There are instances where a single fishing event is associated with two sample ids for the same species (usually no data in one of them) but this results in duplicated fishing events when join_sample_ids = TRUE

https://github.com/pbs-assess/gfdata/blob/master/R/get-dat.R#L261-L267