Cannot create v2 backups: NullPointerException in requireNonNullBlob()

Guidelines

• I have searched open and closed issues for duplicates
• I am submitting a bug report for existing functionality that does not work as intended
• This isn't a feature request or a discussion topic

Bug description

On an old phone, after upgrading to v2 backups, Signal is no longer able to create backups. It used to be able to create "v1" backups (.backup files) without problems.

This is the relevant part of the debug log (I'm not at liberty to share the full debug log, but more information can be provided on request):

[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Class java.lang.Object.getClass()' on a null object reference
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.signal.core.util.CursorExtensionsKt.requireNonNullBlob(CursorExtensions.kt:62)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.database.AttachmentTable.getLocalArchivableAttachments(AttachmentTable.kt:628)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.backup.v2.BackupRepository.$r8$lambda$-JkYeh5kBb-_Hj7tMEfN6Eqopns(BackupRepository.kt:789)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.backup.v2.BackupRepository$$ExternalSyntheticLambda36.invoke(R8$$SyntheticClass:0)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.backup.v2.BackupRepository.export(BackupRepository.kt:1101)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.backup.v2.BackupRepository.exportForLocalBackup(BackupRepository.kt:777)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.backup.v2.local.LocalArchiver.export(LocalArchiver.kt:84)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.jobs.LocalArchiveJob.run(LocalArchiveJob.kt:102)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.jobmanager.JobRunner.run(JobRunner.java:99)
[8.17.4] [4242 ] 2026-07-06 16:13:46.593 GMT+02:00 W LocalArchiveJob:   at org.thoughtcrime.securesms.jobmanager.JobRunner.run(JobRunner.java:62)

This is the relevant part of AttachmentTable.kt:

    617   fun getLocalArchivableAttachments(): List<LocalArchivableAttachment> {
    618     return readableDatabase
    619       .select(*PROJECTION_WITH_METADATA)
    620       .from(TABLE_NAME_WITH_METADTA)
    621       .where("$DATA_HASH_END IS NOT NULL AND $DATA_FILE IS NOT NULL AND ${AttachmentMetadataTable.TABLE_NAME}.${AttachmentMetadataTable.LOCAL_BACKUP_KEY} IS NOT NULL")
    622       .orderBy("$TABLE_NAME.$ID DESC")
    623       .run()
    624       .readToList {
    625         LocalArchivableAttachment(
    626           attachmentId = AttachmentId(it.requireLong(ID)),
    627           file = File(it.requireNonNullString(DATA_FILE)),
    628           random = it.requireNonNullBlob(DATA_RANDOM),
    629           size = it.requireLong(DATA_SIZE),
    630           localBackupKey = AttachmentMetadataTable.getMetadata(it)!!.localBackupKey!!,
    631           plaintextHash = Base64.decode(it.requireNonNullString(DATA_HASH_END)),
    632           contentType = it.requireString(CONTENT_TYPE)
    633         )
    634       }
    635   }

The phone contains old attachments that are encrypted with ClassicDecryptingPartInputStream. For these attachments, the DATA_RANDOM column is NULL. I expect this is the problem.

Would it be possible to fix this one way or the other so that Signal on this phone can create backups again?

Thanks.

Screenshots

No response

Device

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Android version

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Signal version

No response

Link to debug log

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Start in AttachmentTable.kt at getLocalArchivableAttachments(), then read CursorExtensions.kt around requireNonNullBlob() and the BackupRepository.kt export path shown in the stack trace. Reproduce or inspect backup creation with legacy attachments whose DATA_RANDOM is NULL; done means v2 local backups complete without this exception, with appropriate coverage if existing backup tests are found.