Tree widget does not keep selected values opened when adding new values

[tfrancart]

1. Select values from a tree, e.g. "Person > Category" in https://sparnatural.eu/demos/demo-dbpedia-v2/
2. Click on "+" to add another value : normally the tree should open with the value already selected being checked

This is also a problem when loading values from a saved query in a tree widget. Values can be set, but the tree cannot open to view the selected values.