small fix

lib/models/category.dart

@@ -19,7 +19,7 @@ class Category {
   Category.fromJson(Map<String, dynamic> json) {
     id = json['id'];
     name = json['name'];
-    forItemType = json['forItemType'];
+    forItemType = ItemType.values[json['forItemType'] ?? 0];
   }
 
   Category.fromJsonV1(Map<String, dynamic> json) {
@@ -33,5 +33,5 @@ class Category {
   }
 
   Map<String, dynamic> toJson() =>
-      {'id': id, 'name': name, 'forItemType': forItemType};
+      {'id': id, 'name': name, 'forItemType': forItemType.index};
 }

lib/models/history.dart

@@ -34,7 +34,7 @@ class History {
     chapterId = json['chapterId'];
     date = json['date'];
     id = json['id'];
-    itemType = json['itemType'];
+    itemType = ItemType.values[json['itemType'] ?? 0];
     mangaId = json['mangaId'];
   }
 
@@ -54,7 +54,7 @@ class History {
         'chapterId': chapterId,
         'date': date,
         'id': id,
-        'itemType': itemType,
+        'itemType': itemType.index,
         'mangaId': mangaId
       };
 }

lib/models/manga.dart

@@ -87,7 +87,7 @@ class Manga {
     id = json['id'];
     imageUrl = json['imageUrl'];
     isLocalArchive = json['isLocalArchive'];
-    itemType = ItemType.values[json['itemType']];
+    itemType = ItemType.values[json['itemType'] ?? 0];
     lang = json['lang'];
     lastRead = json['lastRead'];
     lastUpdate = json['lastUpdate'];

lib/models/source.dart

@@ -171,7 +171,7 @@ class Source {
         'isAdded': isAdded,
         'isFullData': isFullData,
         'isManga': isManga,
-        'itemType': itemType,
+        'itemType': itemType.index,
         'isNsfw': isNsfw,
         'isPinned': isPinned,
         'lang': lang,