There's no more risk than before. Both versions of the code add two lists together, the other one just ran into Qt Quick type bullshit where one list got serialized to a string.

In terms of what the risk of dupes is: There's one base model with a data role for "is this selected or not" and two filter models which filter this base model based on this data role, in opposite ways. The list in the add dialog is therefore guaranteed not to contain anything that's already selected.