create warning when data not saved to final table

[Paul-Carvalho]

If variables are created after saving 'final table' to fishset (in the define alternatives tab), the model cannot be saved or run. Eg, if I scale landings variable after saving the final table, I wouldn't be able to use that in the model unless I save the final table again.

In this case, I think we should make if easy on the user and generate a popup window to save the final table again without having to go back to define alternatives tab.