We use Examine to index a database with rule definitions. Recently I became aware that for a basic search phrase, such as "admission motion" works fine, but as soon as I add a two character word in the middle such as "admission on motion", we get a NULL reference error:

[NullReferenceException: Object reference not set to an instance of an object.]
   Lucene.Net.Search.BooleanQuery.Rewrite(IndexReader reader) +353
   Lucene.Net.Search.BooleanQuery.Rewrite(IndexReader reader) +367
   Lucene.Net.Search.IndexSearcher.Rewrite(Query original) +29
   Lucene.Net.Search.Query.Weight(Searcher searcher) +52
   Lucene.Net.Search.Searcher.Search(Query query, Filter filter, Int32 n, Sort sort) +29
   Examine.LuceneEngine.SearchResults.DoSearch(Query query, IEnumerable`1 sortField) +258
   Examine.LuceneEngine.Providers.BaseLuceneSearcher.Search(ISearchCriteria searchParams) +181
   Ethics.DAL.EthicsDB.getSearchedOpinions(String searchPhrase) +3109
   Ethics.Opinions.Page_Load(Object sender, EventArgs e) +682

At first look, I cannot see anything wrong with my code. Thoughts?

    public static DataTable getSearchedOpinions(string searchPhrase)
    {
        searchPhrase = Regex.Replace(searchPhrase, @"[^a-zA-Z0-9'.\s/\*""]{1,40}", String.Empty);
        searchPhrase = searchPhrase.Replace(" & ", " & ");
        searchPhrase = searchPhrase.Replace(" and ", " ");
        searchPhrase = Regex.Replace(searchPhrase, @"\s+", " ");
        string[] splitSearchPhrase = Utilities.Split(searchPhrase, " ", "\"");

        DataTable dt = new DataTable();
        dt.Columns.Add("opinion_ID", typeof(Int32));
        dt.Columns.Add("title", typeof(string));
        dt.Columns.Add("summary", typeof(string));
        dt.Columns.Add("bodytext", typeof(string));
        dt.Columns.Add("opinionDate", typeof(DateTime));
        dt.Columns.Add("smallOpinionDate", typeof(string));
        dt.DefaultView.Sort = "opinion_ID DESC";

        Examine.SearchCriteria.IBooleanOperation filter = null;

        int i = 0;

        var criteria2 = ExamineManager.Instance
        .SearchProviderCollection["EthicsOpinionsSearcher"]
        .CreateSearchCriteria();

        filter = null;

        i = 0;
        for (i = 0; i < splitSearchPhrase.Length; i++)
        {
            if (filter == null)
            {
                filter = criteria2
                .GroupedOr(new string[] { "opinion_Num", "title", "summary", "bodytext", "opiniondate", "smallOpinionDate" }, splitSearchPhrase[i].Escape())
                .Or()
                .GroupedOr(new string[] { "title", "summary", "bodytext" }, splitSearchPhrase[i].Fuzzy(0.7f));
            }
            else
            {
                filter = filter
                .And()
                .GroupedOr(new string[] { "title", "summary", "bodytext", "opiniondate" }, splitSearchPhrase[i].Escape())
                .Or()
                .GroupedOr(new string[] { "title", "summary", "bodytext" }, splitSearchPhrase[i].Fuzzy(0.7f));
            }
        }
        ISearchResults SearchResults2 = ExamineManager.Instance.SearchProviderCollection["EthicsOpinionsSearcher"].Search(filter.Compile());

        foreach (var row in SearchResults2)
        {
            DataRow dr = dt.NewRow();
            dr["opinion_ID"] = row.Fields["opinion_ID"];
            dr["title"] = row.Fields["title"];
            dr["summary"] = row.Fields["summary"];
            dr["bodytext"] = row.Fields["bodytext"];
            dr["opinionDate"] = row.Fields["opinionDate"];
            dr["smallOpinionDate"] = row.Fields["smallOpinionDate"];
            dt.Rows.Add(dr);
        }

        return dt;
    }