StatelessKieSession 并发执行  报空指针


java.lang.NullPointerException: null
    at org.drools.core.impl.StatelessKnowledgeSessionImpl.dispose(StatelessKnowledgeSessionImpl.java:395) ~[drools-core-6.1.0.Final.jar:6.1.0.Final]
    at org.drools.core.impl.StatelessKnowledgeSessionImpl.execute(StatelessKnowledgeSessionImpl.java:367) ~[drools-core-6.1.0.Final.jar:6.1.0.Final]
    at org.drools.impl.adapters.StatelessKnowledgeSessionAdapter.execute(StatelessKnowledgeSessionAdapter.java:58) ~[knowledge-api-6.1.0.Final.jar:6.1.0.Final]
    
    
升级 Drools版本 
6.1.0.Final 升级到 6.2.0.Final

某应用 使用 drools 6.5.0.Final ,没有类似问题

ls -al|grep drools
-rw-r--r--    1 dugang  staff   1696673 10 18  2016 drools-compiler-6.5.0.Final.jar
-rw-r--r--    1 dugang  staff   3605246 10 18  2016 drools-core-6.5.0.Final.jar
-rw-r--r--    1 dugang  staff     63719 10 18  2016 drools-decisiontables-6.5.0.Final.jar
-rw-r--r--    1 dugang  staff     32643 10 18  2016 drools-jsr94-6.5.0.Final.jar
-rw-r--r--    1 dugang  staff    127585 10 18  2016 drools-reteoo-6.5.0.Final.jar
-rw-r--r--    1 dugang  staff     59191 10 18  2016 drools-templates-6.5.0.Final.jar