One of the forms of narrations that Al-Amini quotes in his Kitab Al-Ghadir are narrations in which he asks the Companions to admit that they heard the Prophet (peace be upon him) say, “Whosoever I am his mawla then Ali is his mawla.” In these narrations, the Companions claim that they heard no such thing, which causes Ali to beseech Allah to curse them. They are then cursed in various ways, with Anas bin Malik going blind for example and Al-Baraa’ bin ‘Azim getting Vitiligo.
Al-Amini narrates such a report from a Shi’ee source, Rijal Al-Kashshi, which is not an acceptable source of hadith for Sunnis. Through that book, he narrates from Abdul Ghaffar bin Al-Qasim, who was accused of fabricating hadith by Ali bin Al-Madeeni, Abu Dawud Al-Tayalsi, and Abu Dawud Al-Sijistani. See his biography in Lisan Al-Mizan.
Al-Amini also provides another version of the report that includes Jareer bin Abdullah Al-Bajali, which can be found in Ansab Al-Ashraf, however, the chain includes Hisham bin Mohammad bin Al-Sa’ib Al-Kalbi, who was rejected by hadith scholars. Imam Ahmad even said, “I didn’t think that anyone narrated from him.” Ibn Asakir simply said, “He is not trustworthy.” See his biography in Mizan Al-I’itidal.
Al-Tabtaba’ee, who commented on Kitab Al-Ghadir, adds that these reports can also be found in Musnad Ahmad and Tareekh Dimashq. However, these reports, while weak due to the anonymity of Al-Waleed bin Uqba bin Nizar and Eisa bin Muslim. Also, they do not contain the names of those that were cursed.
Al-Amini also provides one other narration from the path of Zathan Abi Omar from Ali that states that he cursed a man that denied him a hadith. That man then went blind. Al-Amini narrates this from Al-Khawarizmi and Al-Mustaghfiri, but both paths include Ammar Al-Hadrami, who is unknown in status.
In conclusion, there are no reliable reports that state that Ali cursed anyone that withheld testifying hearing hadith Al-Ghadir, nor are there any reliable reports that state that anyone withheld a testimony from him in the first place.