Thread:Extension talk:Lucene-search/Internal error in SearchEngine trying to make WikiSearcher: null/reply

This is the whole log of the error.

3812760 [pool-2-thread-43] INFO org.wikimedia.lsearch.frontend.HttpHandler  - query:/search/dev/Haferkleie?namespaces=1156&offset=0&limit=6&version=2.1&iwlimit=10 what:search dbname:dev term:Haferkleie java.lang.NullPointerException at java.util.Hashtable.put(Hashtable.java:411) at org.wikimedia.lsearch.search.WikiSearcher. (WikiSearcher.java:97) at org.wikimedia.lsearch.search.SearchEngine.search(SearchEngine.java:686) at org.wikimedia.lsearch.search.SearchEngine.search(SearchEngine.java:115) at org.wikimedia.lsearch.frontend.SearchDaemon.processRequest(SearchDaemon.java:92) at org.wikimedia.lsearch.frontend.HttpHandler.handle(HttpHandler.java:193) at org.wikimedia.lsearch.frontend.HttpHandler.run(HttpHandler.java:114) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636) 3812762 [pool-2-thread-43] ERROR org.wikimedia.lsearch.search.SearchEngine - Internal error in SearchEngine trying to make WikiSearcher: null java.lang.NullPointerException at java.util.Hashtable.put(Hashtable.java:411) at org.wikimedia.lsearch.search.WikiSearcher. (WikiSearcher.java:97) at org.wikimedia.lsearch.search.SearchEngine.search(SearchEngine.java:686) at org.wikimedia.lsearch.search.SearchEngine.search(SearchEngine.java:115) at org.wikimedia.lsearch.frontend.SearchDaemon.processRequest(SearchDaemon.java:92) at org.wikimedia.lsearch.frontend.HttpHandler.handle(HttpHandler.java:193) at org.wikimedia.lsearch.frontend.HttpHandler.run(HttpHandler.java:114) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603) at java.lang.Thread.run(Thread.java:636)