The drop from ModelExplorer to an ActivityPartition in the diagram is allowed but the inPartition field is not set

Step to reproduce :

1. create an Activity diagram
2. create an ActivityPartition in the diagram
3. create an ActivityNode (eg. CallOperationAction) in the ModelExplorer
4. drop the ActivityNode inside the ActivityPartition

-> this is allowed but neither the inPartition field of the ActivityNode neither the nodes feild of the ActivityPartition are set so the model ii inconsistent with the diagram.

This action should not be possible.