Do nothing when user tries to create "in 0 lessons" due date chip. (#…

…1277)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Bug Fixes**
- Ensured that the "in X lessons" chip is not added if the lesson count
is zero or less.
- **Tests**
- Added tests to validate the correct behavior when no lessons are
specified.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: Nils Reichardt <[email protected]>

app/lib/homework/homework_dialog/homework_dialog.dart

@@ -513,6 +513,9 @@ class _DueDateChipsController extends ChangeNotifier {
   }
 
   void addInXLessonsChip(InXLessonsDueDateSelection inXLessons) {
+    if (inXLessons.inXLessons <= 0) {
+      return;
+    }
     final alreadyExists = chips.firstWhereOrNull(
           (chip) => chip.dueDate == inXLessons,
         ) !=

app/test/homework/homework_dialog_test.dart

@@ -671,6 +671,22 @@ void main() {
       expect(controller.getSelectedLessonChips(), ['Nächste Stunde']);
       expect(nrOfChipsBefore, nrOfChipsAfter);
     });
+    testWidgets(
+        'regression test: when trying to create a custom "in 0 lessons" chip no chip will be added',
+        (tester) async {
+      final controller = createController(tester);
+      controller.addCourse(courseWith(id: 'foo_course'));
+      controller.addNextLessonDates('foo_course', [Date('2023-11-06')]);
+      await pumpAndSettleHomeworkDialog(tester,
+          showDueDateSelectionChips: true);
+
+      final nrOfChipsBefore = controller.getLessonChips().length;
+      await controller.selectCourse('foo_course');
+      await controller.createCustomChip(inXLessons: 0);
+      final nrOfChipsAfter = controller.getLessonChips().length;
+
+      expect(nrOfChipsBefore, nrOfChipsAfter);
+    });
     testWidgets(
         'when creating a "in 5 lessons" custom chip it will be selected and the correct date will be selected',
         (tester) async {