Some queries produce a nullpointer exception

stackTrace = {StackTraceElement[116]@33117} 
 0 = {StackTraceElement@33118} "org.apache.jackrabbit.core.query.lucene.DescendantSelfAxisQuery$DescendantSelfAxisScorer.advance(DescendantSelfAxisQuery.java:520)"
 1 = {StackTraceElement@33119} "org.apache.lucene.search.FilteredQuery$2.score(FilteredQuery.java:157)"
 2 = {StackTraceElement@33120} "org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:581)"
 3 = {StackTraceElement@33121} "org.apache.lucene.search.IndexSearcher.search(IndexSearcher.java:364)"
 4 = {StackTraceElement@33122} "org.hippoecm.repository.query.lucene.HippoSortedLuceneQueryHits.getHits(HippoSortedLuceneQueryHits.java:170)"
 5 = {StackTraceElement@33123} "org.hippoecm.repository.query.lucene.HippoSortedLuceneQueryHits.<init>(HippoSortedLuceneQueryHits.java:125)"
 6 = {StackTraceElement@33124} "org.hippoecm.repository.query.lucene.HippoIndexSearcher.evaluate(HippoIndexSearcher.java:52)"
 7 = {StackTraceElement@33125} "org.apache.jackrabbit.core.query.lucene.JackrabbitIndexSearcher.execute(JackrabbitIndexSearcher.java:96)"
 8 = {StackTraceElement@33126} "org.hippoecm.repository.query.lucene.ServicingSearchIndex.executeQuery(ServicingSearchIndex.java:222)"
 9 = {StackTraceElement@33127} "org.hippoecm.repository.query.lucene.HippoQueryResult.executeQuery(HippoQueryResult.java:74)"
 10 = {StackTraceElement@33128} "org.apache.jackrabbit.core.query.lucene.QueryResultImpl.getResults(QueryResultImpl.java:289)"
 11 = {StackTraceElement@33129} "org.hippoecm.repository.query.lucene.HippoQueryResult.<init>(HippoQueryResult.java:66)"
 12 = {StackTraceElement@33130} "org.hippoecm.repository.query.lucene.ServicingSearchIndex$3.execute(ServicingSearchIndex.java:313)"
 13 = {StackTraceElement@33131} "org.apache.jackrabbit.core.query.QueryImpl$1.perform(QueryImpl.java:132)"
 14 = {StackTraceElement@33132} "org.apache.jackrabbit.core.query.QueryImpl$1.perform(QueryImpl.java:129)"
 15 = {StackTraceElement@33133} "org.apache.jackrabbit.core.session.SessionState.perform(SessionState.java:216)"
 16 = {StackTraceElement@33134} "org.apache.jackrabbit.core.query.QueryImpl.execute(QueryImpl.java:128)"
 17 = {StackTraceElement@33135} "org.hippoecm.repository.impl.QueryDecorator.execute(QueryDecorator.java:429)"
 18 = {StackTraceElement@33136} "org.hippoecm.repository.impl.QueryDecorator.execute(QueryDecorator.java:107)"
 19 = {StackTraceElement@33137} "org.hippoecm.repository.impl.QueryDecorator.execute(QueryDecorator.java:54)"
 20 = {StackTraceElement@33138} "org.hippoecm.hst.content.beans.query.HstQueryImpl.execute(HstQueryImpl.java:376)"
 21 = {StackTraceElement@33139}