我在neo4j数据库中插入很多节点后，在cypher-shell中为节点的chinese_name属性建立了索引，不过并非所有节点都有chinese_name这个属性。 之后在用Java进行嵌入式开发时，执行findNodes()函数时抛出异常，看stacktrace应该是读取索引时出现的问题。后来把索引删除后可以正常执行了。一下是我写的一个测试代码和异常结果。请问这是什么问题呢？ 代码：

private static final File DB_PATH = new File("/home/charlie/Projects/databases/neo4j_demo.db");
private static GraphDatabaseService graphDb;
public static void testGetNode() {
    graphDb = new GraphDatabaseFactory().newEmbeddedDatabase(DB_PATH);
    registerShutdownHook(graphDb);
    try (Transaction tx = graphDb.beginTx()){
        ResourceIterator<Node> iter = graphDb.findNodes(KgEnum.KgLabel.PERSON, "chinese_name", "刘德华");
        if (iter.hasNext()) {
            System.out.println("got one or more nodes");
        } else {
            System.out.println("no node got");
        }
        tx.success();
    } finally {
        graphDb.shutdown();
    }
}

异常信息：

Exception in thread "main" java.lang.UnsupportedOperationException
at org.neo4j.kernel.impl.api.index.AbstractSwallowingIndexProxy.newReader(AbstractSwallowingIndexProxy.java:110)
at org.neo4j.kernel.impl.api.index.FlippableIndexProxy.newReader(FlippableIndexProxy.java:308)
at org.neo4j.kernel.impl.api.index.AbstractDelegatingIndexProxy.newReader(AbstractDelegatingIndexProxy.java:116)
at org.neo4j.kernel.impl.api.IndexReaderFactory$Caching.newUnCachedReader(IndexReaderFactory.java:70)
at org.neo4j.kernel.impl.api.IndexReaderFactory$Caching.newReader(IndexReaderFactory.java:60)
at org.neo4j.kernel.impl.storageengine.impl.recordstorage.StoreStatement.getIndexReader(StoreStatement.java:256)
at org.neo4j.kernel.impl.newapi.AllStoreHolder.indexReader(AllStoreHolder.java:255)
at org.neo4j.kernel.impl.newapi.Read.nodeIndexSeek(Read.java:113)
at org.neo4j.kernel.impl.factory.GraphDatabaseFacade.nodesByLabelAndProperty(GraphDatabaseFacade.java:718)
at org.neo4j.kernel.impl.factory.GraphDatabaseFacade.findNodes(GraphDatabaseFacade.java:593)
at Test.testGetNode(Test.java:65)
at Test.main(Test.java:24)