Automated backup throws an exception

Crowd keeps throwing an exception every night during the automated backup.

2014-02-10 02:00:00,010 scheduler_Worker-1 INFO [crowd.manager.backup.BackupJob] Starting scheduled backup to file atlassian-crowd-2014-02-10-020000-automated-backup-2.7.0.xml...
2014-02-10 02:00:00,385 scheduler_Worker-1 INFO [atlassian.crowd.migration.XmlMigrationManagerImpl] Time taken to export (millis): 375
2014-02-10 02:00:00,385 scheduler_Worker-1 ERROR [org.quartz.core.JobRunShell] Job AutomatedBackup.AutomatedBackup threw an unhandled Exception:
java.lang.NullPointerException
at java.util.Hashtable.put(Hashtable.java:514)
at java.util.Properties.setProperty(Properties.java:161)
at com.atlassian.crowd.dao.directory.DirectoryPropertiesMapper.exportProperties(DirectoryPropertiesMapper.java:222)
at com.atlassian.crowd.file.FileConfigurationExporter.exportDirectories(FileConfigurationExporter.java:26)
at com.atlassian.crowd.manager.backup.DefaultBackupManager.backup(DefaultBackupManager.java:74)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
at com.sun.proxy.$Proxy50.backup(Unknown Source)
at com.atlassian.crowd.manager.backup.BackupJob.executeInternal(BackupJob.java:30)
at org.springframework.scheduling.quartz.QuartzJobBean.execute(QuartzJobBean.java:113)
at org.quartz.core.JobRunShell.run(JobRunShell.java:203)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520)
2014-02-10 02:00:00,385 scheduler_Worker-1 ERROR [org.quartz.core.ErrorLogger] Job (AutomatedBackup.AutomatedBackup threw an exception.
org.quartz.SchedulerException: Job threw an unhandled exception. [See nested exception: java.lang.NullPointerException]
at org.quartz.core.JobRunShell.run(JobRunShell.java:214)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520)

• Nested Exception (Underlying Cause) ---------------
  java.lang.NullPointerException
  at java.util.Hashtable.put(Hashtable.java:514)
  at java.util.Properties.setProperty(Properties.java:161)
  at com.atlassian.crowd.dao.directory.DirectoryPropertiesMapper.exportProperties(DirectoryPropertiesMapper.java:222)
  at com.atlassian.crowd.file.FileConfigurationExporter.exportDirectories(FileConfigurationExporter.java:26)
  at com.atlassian.crowd.manager.backup.DefaultBackupManager.backup(DefaultBackupManager.java:74)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:606)
  at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
  at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:96)
  at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:260)
  at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:94)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
  at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:204)
  at com.sun.proxy.$Proxy50.backup(Unknown Source)
  at com.atlassian.crowd.manager.backup.BackupJob.executeInternal(BackupJob.java:30)
  at org.springframework.scheduling.quartz.QuartzJobBean.execute(QuartzJobBean.java:113)
  at org.quartz.core.JobRunShell.run(JobRunShell.java:203)
  at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520)