NullPointerException When Removing A Version

NullPointerException When remove a version which ever act as a restore point. For example, version 1.1, then I restore to version 1.1, then submit a new version, its name should be 1.1.0. When remove version 1.1, throw NullPointerException. After Investigate code the successors of version 1.1 is null,
original code in removeVerision of JcrVersionHistoryNode:

    predecessors.getValues()
    addValuesNotInSet(successors.getValues(), newNodeSuccessors, versionId, addedValues);
    successors.getValues()
    addValuesNotInSet(predecessors.getValues(), newNodePredecessors, versionId, addedValues);

If I add null check before invoke these method, it function well.