Highlighting fails with NPE for multifield and number_of_fragments:0

[imotov]

To reproduce, start two ES nodes and run the following script:

curl -XDELETE http://localhost:9200/testidx
curl -XPUT http://localhost:9200/testidx -d '{
    "settings" : {
        "index" : {
            "number_of_shards" : 1,
            "number_of_replicas" : 0
        }
    },
    "mappings" : {
        "rec" : {
            "_source" : { "enabled" : false },
            "properties" : {
            "from" : { "type": "string", "store": "yes" }
            }
        }
    }
}'
curl -XPUT http://localhost:9200/testidx/rec/1 -d '{
    "from" : ["user3@test.com","user2@test.com","user5@test.com"]
}'
echo
curl -XPOST http://localhost:9200/testidx/_refresh
echo
curl localhost:9200/testidx/_search -d '{
    "highlight": {
         "fields":{"from":{"number_of_fragments":0}}
    },
    "fields":["*"],
    "size":10,
    "sort":["_score"],
    "query":{
        "query_string":{
            "default_field":"from",
            "query":"*:*"
         }
    }
}' && echo
curl localhost:9201/testidx/_search -d '{
    "highlight": {
         "fields":{"from":{"number_of_fragments":0}}
    },
    "fields":["*"],
    "size":10,
    "sort":["_score"],
    "query":{
        "query_string":{
            "default_field":"from",
            "query":"*:*"
         }
    }
}' && echo

One of the search requests fails and the node where shard is allocated throws the following exception:

[2011-10-07 11:16:57,872][DEBUG][action.search.type       ] [Maha Yogi] [testidx][0], node[czKz17uBQiaTczE_OzQ0GA], [P], s[STARTED]: Failed to execute [org.elasticsearch.action.search.SearchRequest@43233ac]
org.elasticsearch.transport.RemoteTransportException: [Mikhail Rasputin][inet[/10.0.1.8:9300]][search/phase/query+fetch]
Caused by: java.lang.NullPointerException
    at org.elasticsearch.common.io.stream.HandlesStreamOutput.writeUTF(HandlesStreamOutput.java:54)
    at org.elasticsearch.search.highlight.HighlightField.writeTo(HighlightField.java:110)
    at org.elasticsearch.search.internal.InternalSearchHit.writeTo(InternalSearchHit.java:574)
    at org.elasticsearch.search.internal.InternalSearchHits.writeTo(InternalSearchHits.java:246)
    at org.elasticsearch.search.fetch.FetchSearchResult.writeTo(FetchSearchResult.java:101)
    at org.elasticsearch.search.fetch.QueryFetchSearchResult.writeTo(QueryFetchSearchResult.java:90)
    at org.elasticsearch.transport.support.TransportStreams.buildResponse(TransportStreams.java:136)
    at org.elasticsearch.transport.netty.NettyTransportChannel.sendResponse(NettyTransportChannel.java:74)
    at org.elasticsearch.transport.netty.NettyTransportChannel.sendResponse(NettyTransportChannel.java:66)
    at org.elasticsearch.search.action.SearchServiceTransportAction$SearchQueryFetchTransportHandler.messageReceived(SearchServiceTransportAction.java:502)
    at org.elasticsearch.search.action.SearchServiceTransportAction$SearchQueryFetchTransportHandler.messageReceived(SearchServiceTransportAction.java:492)
    at org.elasticsearch.transport.netty.MessageChannelHandler$RequestHandler.run(MessageChannelHandler.java:238)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:680)