Weekly rule without a BYDAY throws an error

[chanan]

Bug description

An rrule like this which is valid: FREQ=WEEKLY;UNTIL=20170324T220000Z;INTERVAL=2 throws an error because _findWeeklyRule (line 1754 of recurrence_helper.dart) return 0 items due to the if (weeklyRule[i].contains('BYDAY'))

According to the iCal spec the above is valid: https://www.kanzaki.com/docs/ical/rrule.html

Steps to reproduce

1. Create an Appointment object with a valid weekly rrule that does not contain a BYDAY section
2. Add it to a datasource of a calendar.

Code sample

Code sample

``` final list = [_Meeting(summary: 'test', from: '2017-02-10 16:00:00:00.000', rrule: 'FREQ=WEEKLY;UNTIL=20170324T220000Z;INTERVAL=2')]; final source = _AppointmentDataSource(source: list);

return SfCalendar(dataSource: source);

</details>

### Screenshots or Video

<details open>
<summary>Screenshots / Video demonstration</summary>

n/a

</details>


### Stack Traces

<details open><summary>Stack Traces</summary>

```dart
The following assertion was thrown building LayoutBuilder:
Invalid weekly recurrence rule
'package:syncfusion_flutter_calendar/src/calendar/appointment_engine/recurrence_helper.dart':
Failed assertion: line 271 pos 12: 'weeklyByDayPos != -1'

The relevant error-causing widget was: 
  SfCalendar SfCalendar:file:///Users/chanan/flutter/bkhome/lib/features/calendar/widgets/calendar_widget.dart:30:12
When the exception was thrown, this was the stack: 
#2      RecurrenceHelper._getWeeklyRecurrenceDateTimeCollection (package:syncfusion_flutter_calendar/src/calendar/appointment_engine/recurrence_helper.dart:271:12)
#3      RecurrenceHelper.getRecurrenceDateTimeCollection (package:syncfusion_flutter_calendar/src/calendar/appointment_engine/recurrence_helper.dart:1072:14)
#4      _SfCalendarState._getMaxAppointmentDate (package:syncfusion_flutter_calendar/src/calendar/sfcalendar.dart:5273:28)
#5      _SfCalendarState.addAgenda (package:syncfusion_flutter_calendar/src/calendar/sfcalendar.dart:6722:16)
#6      _SfCalendarState.build.<anonymous closure> (package:syncfusion_flutter_calendar/src/calendar/sfcalendar.dart:3100:21)
#7      _LayoutBuilderElement._rebuildWithConstraints.updateChildCallback (package:flutter/src/widgets/layout_builder.dart:199:77)
#8      BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:3038:19)
#9      _LayoutBuilderElement._rebuildWithConstraints (package:flutter/src/widgets/layout_builder.dart:239:12)
#10     RenderObject.invokeLayoutCallback.<anonymous closure> (package:flutter/src/rendering/object.dart:2738:59)
#11     PipelineOwner._enableMutationsToDirtySubtrees (package:flutter/src/rendering/object.dart:1108:15)
#12     RenderObject.invokeLayoutCallback (package:flutter/src/rendering/object.dart:2738:14)
#13     RenderConstrainedLayoutBuilder.rebuildIfNecessary (package:flutter/src/widgets/layout_builder.dart:286:5)
#14     _RenderLayoutBuilder.performLayout (package:flutter/src/widgets/layout_builder.dart:377:5)
#15     RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:2465:7)
#16     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:1062:18)
#17     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:1075:15)
#18     RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:609:23)
#19     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:1178:13)
#20     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:475:5)
#21     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1397:15)
#22     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1318:9)
#23     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1176:5)
#24     _invoke (dart:ui/hooks.dart:312:13)
#25     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:427:5)
#26     _drawFrame (dart:ui/hooks.dart:283:31)
(elided 2 frames from class _AssertionError)

On which target platforms have you observed this bug?

macOS

Flutter Doctor output

Doctor output

[✓] Flutter (Channel stable, 3.27.1, on macOS 15.2 24C101 darwin-arm64, locale en-US)
    • Flutter version 3.27.1 on channel stable at /Users/chanan/flutter/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 17025dd882 (2 weeks ago), 2024-12-17 03:23:09 +0900
    • Engine revision cb4b5fff73
    • Dart version 3.6.0
    • DevTools version 2.40.2

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /Users/chanan/Library/Android/sdk
    • Platform android-35, build-tools 34.0.0
    • ANDROID_HOME = /Users/chanan/Library/Android/sdk
    • Java binary at: /Applications/Android Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 21.0.3+-79915917-b509.11)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 16.2)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 16C5032a
    • CocoaPods version 1.14.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2024.2)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 21.0.3+-79915917-b509.11)

[✓] VS Code (version 1.96.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.102.0

[✓] Connected device (5 available)
    • Chanan’s iPhone (mobile)        • 00008140-001201C12EA3001C • ios            • iOS 18.3 22D5034e
    • macOS (desktop)                 • macos                     • darwin-arm64   • macOS 15.2 24C101 darwin-arm64
    • Mac Designed for iPad (desktop) • mac-designed-for-ipad     • darwin         • macOS 15.2 24C101 darwin-arm64
    • Chrome (web)                    • chrome                    • web-javascript • Google Chrome 131.0.6778.205
    • Raspberry Pi 5 (mobile)         • pi-5                      • linux-arm64    • Raspberry Pi 5
    ! Error: Browsing on the local area network for Chanan’s iPhone. Ensure the device is unlocked and attached with a cable or associated with the same local area network as this Mac.
      The device must be opted into Developer Mode to connect wirelessly. (code -27)

[✓] Network resources
    • All expected network resources are available.

• No issues found!

[chanan]

Another valid rrule that fails on int parsing is FREQ=YEARLY;BYMONTH=3;BYDAY=1SA;UNTIL=20241207