my.fbmessenger.android: exclude unsent messages to avoid duplication

my/fbmessenger/android.py

@@ -168,6 +168,15 @@ def _process_db_msys(db: sqlite3.Connection) -> Iterator[Res[Entity]]:
       CAST(sender_id AS TEXT) AS sender_id,
       reply_source_id
     FROM messages
+    WHERE
+        /* Regular message_id conforms to mid.* regex.
+           However seems that when message is not sent yet it doesn't have this server id yet
+           (happened only once, but could be just luck of course!)
+           We exclude these messages to avoid duplication.
+           However poisitive filter (e.g. message_id LIKE 'mid%') feels a bit wrong, e.g. what if mesage ids change or something
+           So instead this excludes only such unsent messages.
+        */
+        message_id != offline_threading_id
     ORDER BY timestamp_ms /* they aren't in order in the database, so need to sort */
         '''
     ):