implemented get hashcode and cleanup

lib/models/ingredient.dart

@@ -16,4 +16,9 @@ class Ingredient {
     Ingredient i = other as Ingredient;
     return title == i.title;
   }
+
+  @override
+  int get hashCode {
+    return Object.hash(title, null);
+  }
 }

lib/models/ingredient_list_entry.dart

@@ -14,4 +14,9 @@ class IngredientListEntry {
     final i = other as IngredientListEntry;
     return ingredient == i.ingredient;
   }
+
+  @override
+  int get hashCode {
+    return Object.hash(ingredient, null);
+  }
 }

lib/widgets/ingredients_bottomsheet.dart

@@ -24,10 +24,10 @@ class _IngredientsBottomsheetState extends State<IngredientsBottomsheet> {
   Unit? selectedUnit;
   final List<DropdownMenuEntry<Unit>> unitEntries = [];
 
-  TextEditingController _amountController = TextEditingController();
+  final TextEditingController _amountController = TextEditingController();
-  TextEditingController _ingredientController = TextEditingController();
+  final TextEditingController _ingredientController = TextEditingController();
   bool _isOptional = false;
-  TextEditingController _unitController = TextEditingController();
+  final TextEditingController _unitController = TextEditingController();
 
   @override
   void initState() {