Facing issue while querying based on the document

[chandresh-pancholi]

Hi,
First of all, I would like to say thank you to the team for writing this plugin. I am trying to integrate it with local ES version 7.4.2
I am getting below failure.

Query:

curl --location --request GET 'localhost:9200/<>/_search' \
--header 'Content-Type: application/json' \
--data-raw '{
    "query": {
        "match_all": {}
    },
    "rescore": {
        "redis": {
            "key_field": "product_id.keyword",
            "key_prefix": "test-"
        }
    }
}'

Caused by: java.lang.NullPointerException
	at org.elasticsearch.index.fielddata.IndexFieldDataService.getForField(IndexFieldDataService.java:115) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.index.query.QueryShardContext.getForField(QueryShardContext.java:191) ~[elasticsearch-7.4.2.jar:7.4.2]
	at com.bigdataboutique.elasticsearch.plugin.RedisRescoreBuilder.innerBuildContext(RedisRescoreBuilder.java:104) ~[?:?]
	at org.elasticsearch.search.rescore.RescorerBuilder.buildContext(RescorerBuilder.java:127) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.search.SearchService.parseSource(SearchService.java:800) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.search.SearchService.createContext(SearchService.java:586) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.search.SearchService.createAndPutContext(SearchService.java:545) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.search.SearchService.executeQueryPhase(SearchService.java:348) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.search.SearchService.lambda$executeQueryPhase$1(SearchService.java:340) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.action.ActionListener.lambda$map$2(ActionListener.java:145) ~[elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.action.ActionListener$1.onResponse(ActionListener.java:62) [elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.search.SearchService.lambda$rewriteShardRequest$7(SearchService.java:1043) [elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.action.ActionRunnable$1.doRun(ActionRunnable.java:45) [elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:44) [elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:773) [elasticsearch-7.4.2.jar:7.4.2]
	at org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:37) [elasticsearch-7.4.2.jar:7.4.2]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
	at java.lang.Thread.run(Thread.java:834) [?:?]