Like Button - Error

ERROR [http-8090-6] [atlassian.event.internal.EventPublisherImpl] invokeListeners There was an exception thrown trying to dispatch event 'com.atlassian.conf
luence.event.events.like.LikeCreatedEvent@7aacb27f[user=EmbeddedCrowdUser{name='USER', displayName='USER', directoryId=1835009},content=page: PAGE v
.2 (21334738),timestamp=1359369813723]' from the invoker 'com.atlassian.event.internal.SingleParameterMethodListenerInvoker@3280d257'.
 -- url: /rest/likes/1.0/content/21334738/likes | userName: USER | referer: http://URL/
java.lang.RuntimeException: Invalid recipient: null
        at com.atlassian.event.internal.SingleParameterMethodListenerInvoker.invoke(SingleParameterMethodListenerInvoker.java:54)
        at com.atlassian.event.internal.AsynchronousAbleEventDispatcher$2.run(AsynchronousAbleEventDispatcher.java:60)
        at com.atlassian.event.internal.AsynchronousAbleEventDispatcher$1.execute(AsynchronousAbleEventDispatcher.java:28)
        at com.atlassian.event.internal.AsynchronousAbleEventDispatcher.dispatch(AsynchronousAbleEventDispatcher.java:56)
        at com.atlassian.event.internal.EventPublisherImpl.invokeListeners(EventPublisherImpl.java:151)
        at com.atlassian.event.internal.EventPublisherImpl.publish(EventPublisherImpl.java:70)
        at com.atlassian.confluence.like.DefaultLikeManager.addLike(DefaultLikeManager.java:63)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:182)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:149)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:106)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
        at com.atlassian.spring.interceptors.SpringProfilingInterceptor.invoke(SpringProfilingInterceptor.java:16)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:171)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
        at $Proxy84.addLike(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)