Do not depend on hard coded variable name "processInstance"

If there is a conditional intermediate catch event in a process definition like this:

processInstance: WorkflowProcessInstance()
objectId: Long() from processInstance.getVariable("workflowObjectId")
o: MyObject(id == objectId, name == "My name")

and it is triggered by updating a fact (MyObject) in the knowledge base it might happen that more than just the one process proceed if the process instance variable isn't named "processInstance". There seems to be some hard coded magic about the variable name "processInstance".