What is the authenticity of the hadiths narrated regarding fasting during the second half of Sha'ban?

No authentic hadith has been reported from the Prophet, peace be upon him, regarding fasting in the middle of Sha‘ban. However, a weak hadith is reported from Ali, may Allah be pleased with him, that the Prophet, peace be upon him, said: "When it is the night of the middle of Sha‘ban, spend its night in prayer and fast its day. For indeed, Allah descends therein at sunset to the lowest heaven and says: 'Is there anyone seeking forgiveness that I may forgive him? Is there anyone seeking sustenance that I may provide for him? Is there such and such? Is there such and such?' until dawn rises." Scholars have deemed this hadith weak; some even considered it fabricated.