NPE in OneComparatorFieldValueHitQueue.lessThan while indexing

I get occasionally this NPE while searching and the Solr process finishes.

23-oct-2018 15:04:50 INFO: [Products] webapp=/solr path=/select params={q=:&facet.limit=10000&spellcheck.maxResultsForSuggest=0&spellcheck=true&fl=ID,LAST_MODIFIED,INDEXED&start=2300000&facet.mincount=1&sort=ID+asc&rows=100000&facet.sort=index} hits=4598058 status=0 QTime=6958
23-oct-2018 15:04:56 SEVERE: java.lang.NullPointerException
at org.apache.lucene.search.FieldValueHitQueue$OneComparatorFieldValueHitQueue.lessThan(FieldValueHitQueue.java:56)
at org.apache.lucene.util.PriorityQueue.downHeap(PriorityQueue.java:284)
at org.apache.lucene.util.PriorityQueue.pop(PriorityQueue.java:184)
at org.apache.lucene.search.TopFieldCollector.populateResults(TopFieldCollector.java:425)
at org.apache.lucene.search.TopDocsCollector.topDocs(TopDocsCollector.java:156)
at org.apache.solr.search.SolrIndexSearcher.getDocListNC(SolrIndexSearcher.java:1585)
at org.apache.solr.search.SolrIndexSearcher.getDocListC(SolrIndexSearcher.java:1399)
at org.apache.solr.search.SolrIndexSearcher.search(SolrIndexSearcher.java:566)
at org.apache.solr.handler.component.QueryComponent.process(QueryComponent.java:545)
at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:296)
at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:173)
at org.apache.solr.core.SolrCore.execute(SolrCore.java:2477)
at org.apache.solr.servlet.HttpSolrCall.execute(HttpSolrCall.java:723)
at org.apache.solr.servlet.HttpSolrCall.call(HttpSolrCall.java:529)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:361)
at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:305)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1691)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:582)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:548)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1180)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:512)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1112)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:213)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:119)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:134)
at org.eclipse.jetty.server.Server.handle(Server.java:534)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:320)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:251)
at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:273)
at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:95)
at org.eclipse.jetty.io.SelectChannelEndPoint$2.run(SelectChannelEndPoint.java:93)
at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.executeProduceConsume(ExecuteProduceConsume.java:303)
at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.produceConsume(ExecuteProduceConsume.java:148)
at org.eclipse.jetty.util.thread.strategy.ExecuteProduceConsume.run(ExecuteProduceConsume.java:136)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:671)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:589)
at java.lang.Thread.run(Thread.java:745)