Protected against crash with unread counter that exceeds thread size.

app/src/main/java/org/thoughtcrime/securesms/conversation/v2/ConversationItemDecorations.kt

@@ -109,10 +109,11 @@ class ConversationItemDecorations(hasWallpaper: Boolean = false, private val sch
    * which causes the unread divider to be removed.
    */
   private fun updateUnreadState(items: List<ConversationElement?>) {
-    val state = unreadState
+    val state: UnreadState = unreadState
 
     if (state is UnreadState.InitialUnreadState) {
-      val timestamp = (items[state.unreadCount - 1] as? ConversationMessageElement)?.timestamp()
+      val firstUnread = items[(state.unreadCount - 1).coerceIn(items.indices)]
+      val timestamp = (firstUnread as? ConversationMessageElement)?.timestamp()
       if (timestamp != null) {
         unreadState = UnreadState.CompleteUnreadState(unreadCount = state.unreadCount, firstUnreadTimestamp = timestamp)
       }

app/src/main/java/org/thoughtcrime/securesms/database/MessageTable.kt

@@ -3285,6 +3285,7 @@ open class MessageTable(context: Context?, databaseHelper: SignalDatabase) : Dat
     }
 
     threadIds.forEach {
+      threads.updateReadState(it)
       threads.update(
         threadId = it,
         unarchive = false,