Now I have solved the problem with java.lang.NullPointerException happened in at org.jbpm.ruleflow.core.validation.RuleFlowProcessValidator.validateNodes(RuleFlowProcessValidator.java:193)
Diverging gateways should have constraints. For further information see the following documentation (chapter 6.8.2 constraints) http://docs.jboss.org/jbpm/v5.4/userguide/ch.core-basics.html#d0e2175