Create empty() factory for word search results

lib/models/word_search/word_search_result.dart

@@ -81,6 +81,18 @@ class WordSearchResult {
         sources: WordSearchSources.fromJson(json['sources']),
       );
 
+  factory WordSearchResult.empty() => WordSearchResult(
+    score: 0,
+    entryId: 0,
+    isCommon: false,
+    japanese: [],
+    kanjiInfo: {},
+    readingInfo: {},
+    senses: [],
+    jlptLevel: JlptLevel.none,
+    sources: WordSearchSources.empty(),
+  );
+
   String _formatJapaneseWord(WordSearchRuby word) =>
       word.furigana == null ? word.base : '${word.base} (${word.furigana})';
 

lib/models/word_search/word_search_sources.dart

@@ -9,6 +9,8 @@ class WordSearchSources {
 
   const WordSearchSources({this.jmdict = true, this.jmnedict = false});
 
+  factory WordSearchSources.empty() => const WordSearchSources();
+
   Map<String, Object?> get sqlValue => {'jmdict': jmdict, 'jmnedict': jmnedict};
 
   Map<String, dynamic> toJson() => {'jmdict': jmdict, 'jmnedict': jmnedict};