Is the fast valid for someone who dreamt of masturbating without ejaculation while fasting in Ramadan, knowing that he did not perform ghusl?

Your fast is valid because no semen was discharged from you during the daytime while fasting. However, you must offer sincere repentance for this bad habit, and its gravity intensifies during Ramadan because it is a month of worship and obedience. To get rid of it, please refer to Fatwa no. 33352.