NullPointerException in MoveNonPictureProfileAttachmentsUpgradeTask

After upgrading Confluence from 2.1.5a to 2.2.1 Build 514, the following exception can be thrown. Anyways, when the server was up and running again, the pictures seems to be OK after all.

java.lang.NullPointerException
at com.atlassian.confluence.upgrade.MoveNonPictureProfileAttachmentsUpgradeTask.doUpgrade(MoveNonPictureProfileAttachmentsUpgradeTask.java:67)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.springframework.aop.framework.AopProxyUtils.invokeJoinpointUsingReflection(AopProxyUtils.java:61)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:149)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:116)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:56)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:138)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:152)
at $Proxy40.doUpgrade(Unknown Source)