Designer / Page Provider / form / nuxeo-dropdown-aggregate do not generate properly

Reproduction steps
In Studio
1. Create a new Document Type
1. Add a property type string or whatever
1. Create a Page provider with an aggregate targeting that property
1. Generate the form and the results layout associated to the Page provider in the Designer
1. Add a new search menu on the left side, bounded to that Page provider
In your Nuxeo instance
1. Create a couple document of the previously created type
1. Search using for any of the value selected in the aggregate
1. => No filter is applied
Behavior:
While generating the form corresponding to an aggregate defined in the modeler, the page provider using the aggregate does not filter the documents properly.
Workaround:
Add the property multiple at true in the designer.
Expected:
Generate the nuxeo-dropdown-aggregate with the property multiple at true.