Fix various backup import-export inconsistencies.

app/src/main/java/org/thoughtcrime/securesms/attachments/TombstoneAttachment.kt

@@ -48,6 +48,7 @@ class TombstoneAttachment : Attachment {
     width: Int?,
     height: Int?,
     caption: String?,
+    fileName: String? = null,
     blurHash: String?,
     voiceNote: Boolean = false,
     borderless: Boolean = false,
@@ -59,7 +60,7 @@ class TombstoneAttachment : Attachment {
     quote = quote,
     transferState = AttachmentTable.TRANSFER_PROGRESS_PERMANENT_FAILURE,
     size = 0,
-    fileName = null,
+    fileName = fileName,
     cdn = Cdn.CDN_0,
     remoteLocation = null,
     remoteKey = null,