Do not add mangas to the default category (#433)

The default category is used as a fallback and should never be actually mapped to mangas in the database.
However, when using the update manga category mutation the server still creates this mapping, which then leads to issues with getting mangas for the default category

src/components/manga/MangaDetails.tsx

@@ -169,7 +169,9 @@ export const MangaDetails: React.FC<IProps> = ({ manga }) => {
     const { t } = useTranslation();
     const { data: categoriesData, loading: areCategoriesLoading } = requestManager.useGetCategories();
     const categories = categoriesData?.categories.nodes ?? [];
-    const defaultCategoryIds = categories.filter((category) => category.default).map((category) => category.id);
+    const defaultCategoryIds = categories
+        .filter((category) => category.default && category.id !== 0)
+        .map((category) => category.id);
     const [updateMangaCategories] = requestManager.useUpdateMangaCategories();
 
     useEffect(() => {