checkDuplicatesInProduction fails when primary key field is empty

[zaibquraishi]

specifically occurs for Fish Seines datatype when data for colname='scientificname' is empty in tbl_fish_abundance_data

[r7butler]

@zaibquraishi can you check this again? i made some changes to that checkDuplicatesInProduction function (issue #27 ) i am thinking that fix may have also unintentionally corrected this one maybe