#370 Issues with the model editor handling literature

[Miguel de Alba Aparicio]

I tested 6 different use cases assigning literature items to the primary and secondary models with the model editor node. 3 use cases gave me errors:
1. (Secondary model) Adding 2 literature item to the estimated model results in 1 literature item for the estimated model and 1 for the model
2. (Secondary model) Adding 2 literature item to the model results in 1 literature item for the estimated model and 1 for the model
3. (Primary model) Adding 2 literature items to the model results in no literature items.

[Armin Weiser]

fixed, please re-check