From al-Malfūdh Sharīf, Pg 95:

Question: What is the ruling of the Shari’ah on a person who performed the Salāt al-Janāzah of a Wahābī that prescribed to anti-Islamic beliefs?

Answer: There is no Salāt al-Janāzah for a Wahābī, Rāfdī, Qadiyānī all heretics whose Kufr has been established, Salāt al-Janāzah is for a Muslim who holds correct Islamic beliefs and not for the Kuf’fār or an apostate. After knowing this fact and to still read Salāt al-Janāzah for such a person is kufr