word_search: don't throw error on empty results

lib/search/word_search/entry_id_query.dart

@@ -77,7 +77,7 @@ String _filterFTSSensitiveCharacters(String word) {
             ${!countOnly ? 'LIMIT ?' : ''}
           )
 
-        ${countOnly ? 'SELECT COUNT("entryId") AS count' : 'SELECT "entryId", MAX("score") AS "score"'}
+        SELECT ${countOnly ? 'COUNT("entryId") AS count' : '"entryId", MAX("score") AS "score"'}
         FROM (
           SELECT * FROM fts_results
           UNION
@@ -128,7 +128,7 @@ Future<int> _queryKanjiCount(
   );
   return connection
       .rawQuery(query, args)
-      .then((result) => result.first['count'] as int);
+      .then((result) => result.firstOrNull?['count'] as int? ?? 0);
 }
 
 Future<List<ScoredEntryId>> _queryKana(
@@ -161,7 +161,7 @@ Future<int> _queryKanaCount(
   );
   return connection
       .rawQuery(query, args)
-      .then((result) => result.first['count'] as int);
+      .then((result) => result.firstOrNull?['count'] as int? ?? 0);
 }
 
 Future<List<ScoredEntryId>> _queryEnglish(