Does the prayer of a latecomer become nullified if he stands up before the Imam says the first Tasleem?

It is permissible for someone who joined the prayer late (masbuq) to stand up to complete what he missed after his Imam pronounces the first tasleem, though it is more preferable for him to wait for the second tasleem. However, if he stands up before the Imam’s first tasleem, his prayer is invalid.

The Malikis stated that the masbuq should stand up after the Imam’s tasleem, otherwise his prayer becomes void. As for the Shafi'is, they recommended that he should not stand up until the Imam has completed both tasleems, but it is permissible for him to stand up after the first tasleem because the Imam has exited the prayer with it. If he stands up before the Imam begins either of the two tasleems, his prayer is invalid.