[flutter_local_notifications] setupAlarm method: handle ScheduleMode.…

…useAllowWhileIdle() called on null (#2199)

* Handle ScheduleMode.useAllowWhileIdle() called on a null object reference

* handle null: added scheduleMode = ScheduleMode.exact

* added semicolon

* fixed typo in comments

---------

Co-authored-by: Michael Bui <25263378+MaikuB@users.noreply.github.com>

flutter_local_notifications/android/src/main/java/com/dexterous/flutterlocalnotifications/FlutterLocalNotificationsPlugin.java

@@ -598,7 +598,7 @@ private static void scheduleNextRepeatingNotification(
     AlarmManager alarmManager = getAlarmManager(context);
     if (notificationDetails.scheduleMode == null) {
       // This is to account for notifications created in older versions prior to allowWhileIdle
-      // being added so the deserialiser.
+      // being added to the deserialiser.
       // Reference to old behaviour:
       // https://github.com/MaikuB/flutter_local_notifications/blob/4b723e750d1371206520b10a122a444c4bba7475/flutter_local_notifications/android/src/main/java/com/dexterous/flutterlocalnotifications/FlutterLocalNotificationsPlugin.java#L569C37-L569C37
       notificationDetails.scheduleMode = ScheduleMode.exactAllowWhileIdle;
@@ -676,7 +676,7 @@ private static void repeatNotification(
 
     if (notificationDetails.scheduleMode == null) {
       // This is to account for notifications created in older versions prior to allowWhileIdle
-      // being added so the deserialiser.
+      // being added to the deserialiser.
       // Reference to old behaviour:
       // https://github.com/MaikuB/flutter_local_notifications/blob/4b723e750d1371206520b10a122a444c4bba7475/flutter_local_notifications/android/src/main/java/com/dexterous/flutterlocalnotifications/FlutterLocalNotificationsPlugin.java#L642
       notificationDetails.scheduleMode = ScheduleMode.inexact;
@@ -700,6 +700,15 @@ private static void setupAlarm(
       AlarmManager alarmManager,
       long epochMilli,
       PendingIntent pendingIntent) {
+
+    if (notificationDetails.scheduleMode == null) {
+      // This is to account for notifications created in older versions prior to allowWhileIdle
+      // being added to the deserialiser.
+      // Reference to old behaviour:
+      // https://github.com/MaikuB/flutter_local_notifications/blob/master/flutter_local_notifications/android/src/main/java/com/dexterous/flutterlocalnotifications/FlutterLocalNotificationsPlugin.java#L735
+      notificationDetails.scheduleMode = ScheduleMode.exact;
+    }
+
     if (notificationDetails.scheduleMode.useAllowWhileIdle()) {
       setupAllowWhileIdleAlarm(notificationDetails, alarmManager, epochMilli, pendingIntent);
     } else {