A person performed ṣalāt-ul-witr on their own. They forgot to recite the du’ā of qunūt in the third rak’ah and performed rukū’. They then remembered that they had missed the du’ā of qunūt, so they stood back up and recited the du’ā of qunūt. They performed rukū’ again a second time and completed ṣalāh, performing sujūd-us-sahw at the end. Is their ṣalāh valid?