For the actual master/kepler branch (2.7.0.xxx) of the modeler.

Procedure:
responding to the diagram view

*) Loading a BPMN Model in the Modeler.
*) Select the background / the process and showing its properties.
it is possible to delete the process by hitting delete
*) just the process is deleted, all tasks gateways etc... still remain
*) undo the delete operation
*) after the undo operation selecting a task etc. results in a NullpointerException