title: when query by index in Neo4j, partial results get NaN lucene score
body: <p>In neo4j, I use custom analyzer to build lucene index. However, when search in index, some of the query result get a NaN score.</p>
  
  <p>source code:</p>
  
  <pre><code>try (Transaction tx = Neo4j.graphDb.beginTx()) {
          IndexManager index = Neo4j.graphDb.index();
          /**query*/
          Index&lt;Node&gt; addressNodeFullTextIndex = index.forNodes("NodeFullTextIndex",
                  MapUtil.stringMap(IndexManager.PROVIDER, "lucene", "analyzer", IKAnalyzer5x.class.getName()));
          Query test = IKQueryParser.parseMultiField(fields, query);
          IndexHits&lt;Node&gt; foundNodes = addressNodeFullTextIndex.query(test);
  
          for(Node n : foundNodes){
              Map&lt;String, Object&gt; m = n.getAllProperties();
              m.put("score", foundNodes.currentScore());
              log.info("method[selectByIndex] score&lt;"+foundNodes.currentScore()+"&gt;");
              ret.add(m);
  
          }
          tx.success();
      } catch (IOException e) {
          log.error("method[selectByIndex] fields&lt;"+Joiner.on(",").join(fields)+"&gt; query&lt;"+query+"&gt;", e);
          throw e;
      }
  </code></pre>
  
  <p>and that's the result json:</p>
  
  <p><code>[
     {
        "score":4.786232,
        "knowledge_name":"信阳市科学技术局",
        "knowledge_id":"baidubaike_4658797/4658797"
     },
     {
        "score":1.4323579,
        "knowledge_name":"信阳市人事局",
        "knowledge_id":"baidubaike_4658842/4658842"
     },
     {
        "score":NaN,
        "knowledge_name":"信阳市农业局",
        "knowledge_id":"baidubaike_4658885/4658885"
     }
  ]</code></p>
  
  <p>neo4j version: 3.1.0
  Lucene version: 5.5.0</p>
  
  <p>you can see some score code get a NaN value, why? Or is there something wrong in the query code?</p>