I did this query:

fullTextQuery.setFirstResult(sr.getOffset());
fullTextQuery.setMaxResults(sr.getLength());
List results = fullTextQuery.list();

sr.getOffset() and sr.getLength() are pagination parameters. They happened to be carried from another query as a session properties (not the right thing to do here but it happened). In my case offset was 10 and length was 10. The new search result is empty, so these lines of code in FullTextQueryImpl gave a negative capacity for list exception:

int first = first();
int max = max( first, hits );
Session sess = (Session) this.session;
List<EntityInfo> infos = new ArrayList<EntityInfo>( max - first + 1);

because max=-1 and first=10. Would it be nice if a check is done before assign List capacities?