made changes to the recipe class

lib/models/recipe.dart

@@ -13,8 +13,8 @@ class Recipe {
   final Duration cookTime;
   final Duration totalTime;
   final List<String> keywords;
-  final MealCategory mealCategory;
-  final Cuisine cuisine;
+  final MealCategory? mealCategory;
+  final Cuisine? cuisine;
 
   Recipe({
     this.id = -1,
@@ -25,8 +25,8 @@ class Recipe {
     this.prepTime = const Duration(),
     this.cookTime = const Duration(),
     this.totalTime = const Duration(),
-    this.mealCategory = MealCategory.notSelected,
-    this.cuisine = Cuisine.notSelected,
+    this.mealCategory,
+    this.cuisine,
     this.ingredients = const [],
     this.keywords = const [],
     this.steps = const [],