Crash when making a backup

Start with SaveAttachmentTask.java, especially the doInBackground and saveAttachment calls at lines 81 and 132 shown in the debug log. Reproduce the backup flow on Android 11 and trace the reported file-creation failure. Done means Signal completes the backup without crashing and creates the backup file.

• I have searched open and closed issues for duplicates
• I am submitting a bug report for existing functionality that does not work as intended
• I have read https://github.com/signalapp/Signal-Android/wiki/Submitting-useful-bug-reports
• This isn't a feature request or a discussion topic

Bug description

Signal Crashes when at the end of taking a Backup. No Backup File is created.

Steps to reproduce

• Create a Backup

Actual result: Signal crashes
Expected result: Backup File should be created

Device info

Device: Motorola Moto G Pro
Android version: 11
Signal version: 5.9.7

Link to debug log

https://debuglogs.org/d69de3cd3ee5e48f3b4d6750e1e9d11a3a1bb580d0e94a3a71c6d46ff162463c

Relevant Part I think:

[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: java.lang.RuntimeException: An error occurred while executing doInBackground()
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.os.AsyncTask$4.done(AsyncTask.java:415)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at java.util.concurrent.FutureTask.run(FutureTask.java:271)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at java.lang.Thread.run(Thread.java:923)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: Caused by: java.lang.IllegalStateException: Failed to build unique file: /storage/emulated/0/Pictures/image.png bucket_display_name=Pictures volume_name=external_primary date_modified=null date_expires=null _display_name=image.png mime_type=image/png _data=/storage/emulated/0/Pictures/image.png _size=null is_trashed=0 is_pending=0 bucket_id=-1617409521 relative_path=Pictures/
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.os.Parcel.createExceptionOrNull(Parcel.java:2381)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.os.Parcel.createException(Parcel.java:2357)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.os.Parcel.readException(Parcel.java:2340)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:190)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:142)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.content.ContentProviderProxy.update(ContentProviderNative.java:649)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.content.ContentResolver.update(ContentResolver.java:2356)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.content.ContentResolver.update(ContentResolver.java:2318)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at org.thoughtcrime.securesms.util.SaveAttachmentTask.saveAttachment(SaveAttachmentTask.java:132)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at org.thoughtcrime.securesms.util.SaveAttachmentTask.doInBackground(SaveAttachmentTask.java:81)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at org.thoughtcrime.securesms.util.SaveAttachmentTask.doInBackground(SaveAttachmentTask.java:38)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at android.os.AsyncTask$3.call(AsyncTask.java:394)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
[5.9.7] [263444] 2021-05-10 12:17:14.621 GMT+02:00 E SignalUncaughtException: 	... 3 more