Error checkpoints for calc_size_stratum_BS/AIGOA(): unavailable data

[zoyafuso-NOAA]

• [x] Put an error if you don’t have a size list in your data
• [x] Put an error if you have invertebrates
• [x] Put an error when you don’t have unsexed individuals.
• [x] Error when characters are used in GROUP column (message: no rows to aggregate)
• [x] Add units to the length column “LENGTH_MM”