Task does not allow multiple incoming sequence flow (uncontrolled flow)

Issue

• According to BPMN 2.0 specification allows on page 153 multiple incoming flow sequences for activities (i.e. also for tasks). jBPM fails to validate such an BPMN file. It throws an IllegalArgumentException with the message This type of node cannot have more than one incoming connection!.
• jBPM Web Designer and the Eclipse BPMN2 modeller BPMN2 Diagram Editor currently does not allow multiple incoming connections for User Task . How to do that?