Currently, the error message of the interface ProdutoExportacaoImportacaoEspecificacaoV2.aspx in the catalog import/export, when a user is trying to export a product specification sheet and there are no products in a given category (but there are specifications registered) do not point out the origin of the problem.

The message shown is a very generic exception:

Ocorreu algo inesperado: Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

It should be something in the lines of:

"There are no products in this category". 

1. Access the ProdutoExportacaoImportacaoEspecificacaoV2.aspx interface.
2. Export a product specification sheet that has product fields registered but no products in it.

There are no workarounds.