Crash in edit dialog for CalDAV event with attendees

[min7-i]

Checklist

• [x] I can reproduce the bug with the latest version.
• [x] I made sure that there are no existing issues - open or closed - to which I could contribute my information to.
• [x] I have read the FAQ and my problem isn't listed.
• [x] I have taken the time to fill in all the required details. I understand that the bug report will be dismissed otherwise.
• [x] This issue contains only one bug.
• [x] I have read and understood the contribution guidelines.

Describe the bug For a CalDAV event with attendees the app crashes in the edit dialog when opening the time zone selector or when switching back and forth between the calendar app and other apps.

To Reproduce Steps to reproduce the behavior:

1. Make sure that "CalDAV sync" and "Allow changing event time zones" are checked in settings.
2. Open the edit dialog for a CalDAV event that has attendees.
3. Tap on the time zone.
4. The app crashes.

Expected behavior The time zone list is displayed without any crash happening. / Switching between the calendar app and other apps doesn't cause any crashes.

Screenshots N/A (see crash log below)

Device info (please complete the following information):

• Model: Google Pixel 6a
• OS: Android 14 (GrapheneOS)
• Version: 1.0.2

Additional context

crash log

type: crash
osVersion: google/bluejay/bluejay:14/UQ1A.240105.002/2024010400:user/release-keys
package: org.fossify.calendar:3
process: org.fossify.calendar
processUptime: 6210 + 187 ms
installer: com.android.packageinstaller

android.os.BadParcelableException: Parcelable encountered IOException writing serializable object (name = org.fossify.calendar.models.Event)
	at android.os.Parcel.writeSerializable(Parcel.java:2799)
	at android.os.Parcel.writeValue(Parcel.java:2565)
	at android.os.Parcel.writeValue(Parcel.java:2364)
	at android.os.BaseBundle.dumpStats(BaseBundle.java:1919)
	at android.os.BaseBundle.dumpStats(BaseBundle.java:1956)
	at android.app.servertransaction.PendingTransactionActions$StopInfo.collectBundleStates(PendingTransactionActions.java:123)
	at android.app.servertransaction.PendingTransactionActions$StopInfo.run(PendingTransactionActions.java:139)
	at android.os.Handler.handleCallback(Handler.java:958)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loopOnce(Looper.java:205)
	at android.os.Looper.loop(Looper.java:294)
	at android.app.ActivityThread.main(ActivityThread.java:8279)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:552)
	at com.android.internal.os.ExecInit.main(ExecInit.java:49)
	at com.android.internal.os.RuntimeInit.nativeFinishInit(Native Method)
	at com.android.internal.os.RuntimeInit.main(RuntimeInit.java:359)
Caused by: java.io.NotSerializableException: org.fossify.calendar.models.Attendee
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1240)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:354)
	at java.util.ArrayList.writeObject(ArrayList.java:873)
	at java.lang.reflect.Method.invoke(Native Method)
	at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1079)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1568)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1490)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1234)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1620)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1581)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1490)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1234)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:354)
	at android.os.Parcel.writeSerializable(Parcel.java:2794)
	... 16 more