java.lang.IllegalStateException: No active FlowSession to access; this FlowExecution has ended

2019-03-05 10:05:16,457 - [http-bio-8077-exec-3] -Error getting service from flow state.
java.lang.IllegalStateException: No active FlowSession to access; this FlowExecution has ended
    at org.springframework.webflow.engine.impl.FlowExecutionImpl.getActiveSession(FlowExecutionImpl.java:191) [spring-webflow-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.springframework.webflow.engine.impl.RequestControlContextImpl.getFlowScope(RequestControlContextImpl.java:134) ~[spring-webflow-2.3.0.RELEASE.jar:2.3.0.RELEASE]
    at org.jasig.cas.web.support.WebUtils.getService_aroundBody8(WebUtils.java:89) ~[cas-server-core-3.6.1.0.jar:3.6.1.0]
    at org.jasig.cas.web.support.WebUtils.getService_aroundBody9$advice(WebUtils.java:57) ~[cas-server-core-3.6.1.0.jar:3.6.1.0]
    at org.jasig.cas.web.support.WebUtils.getService(WebUtils.java:1) ~[cas-server-core-3.6.1.0.jar:3.6.1.0]

cas自己的bug，不影响单点登录