Handle case where there are no messages

app/src/main/java/org/thoughtcrime/securesms/database/MmsSmsDatabase.java

@@ -325,11 +325,14 @@ public class MmsSmsDatabase extends Database {
     String selection = MmsSmsColumns.THREAD_ID + " = " + threadId;
 
     try (Cursor cursor = queryTables(PROJECTION, selection, order, "1")) {
-      cursor.moveToFirst();
+      if (cursor.moveToFirst()) {
         return cursor.getLong(cursor.getColumnIndexOrThrow(MmsSmsColumns.NORMALIZED_DATE_SENT));
       }
     }
 
+    return -1;
+  }
+
   public Cursor getUnread() {
     String order           = MmsSmsColumns.NORMALIZED_DATE_SENT + " ASC";
     String selection       = "(" + MmsSmsColumns.READ + " = 0 OR " + MmsSmsColumns.REACTIONS_UNREAD + " = 1) AND " + MmsSmsColumns.NOTIFIED + " = 0";

app/src/main/java/org/thoughtcrime/securesms/database/ThreadDatabase.java

@@ -939,8 +939,10 @@ public class ThreadDatabase extends Database {
       if (count > 0) {
         MmsSmsDatabase mmsSmsDatabase = DatabaseComponent.get(context).mmsSmsDatabase();
         long messageTimestamp = mmsSmsDatabase.getLastMessageTimestamp(threadId);
+        if (messageTimestamp > 0) {
           lastMessage = mmsSmsDatabase.getMessageForTimestamp(messageTimestamp);
         }
+      }
 
       return new ThreadRecord(body, snippetUri, lastMessage, recipient, date, count,
                               unreadCount, unreadMentionCount, threadId, deliveryReceiptCount, status, type,