Bukhari declaring a Taba taba'e to be follower of Ibn Saba and then taking Narrations from him

Muhammad bin Isma'el Bukhari (Died 206 AH) says about a grandson of Imam Ali Ibn Abi Talib (as) : 

عبد الله بن محمد ابن الحنفية ومُحَمَّد هو [ابْن] علي بْن أَبِي طالب الَهاشمي أَبُو هاشم أخو الْحَسَن، سَمِعَ أباه، يُعَدُّ في أَهْلِ الْمَدِينَةِ، قَالَ عَبْد اللَّه بْن مُحَمَّد - عَنِ ابْن عُيَيْنَةَ حَدَّثَنَا الزُّهْرِيّ: كَانَ الْحَسَن أوثقهما في أنفسنا، وكَانَ عَبْد اللَّه يتبع السبائية. 

Abdullah bin Muhammad bin Al- Hanafiyyah, He was grandson of Ali Ibn Abi Talib Al-Hashmi, Abu Hashim, Brother of Hasan. He heard from his father narrations. He was from Medina. Abdullah bin Muhammad narrated from Ibn Uyunah from Zuhri who said that : Hasan was more reliable among the two brothers. This Abdullah (bin Muhammad bin Al-Hanafiyyah) was follower of Abdullah bin Saba.

Kitab Tarikh Al-Kabir - Bukhari // Volume 5 // Page 187 // Number 582 // Edn. Al-Faruq AlHadeethiyah Cairo Egypt.

But the same Bukhari narrated from him in his Sahih Bukhari.

Sahih Bukhari - Muhammad bin Ismael Bukhari // Page 915 // Number 5115 // Edn. Dar u Salam Riyadh Saudi Arabia.