Can a defendant appeal his own Notice of Appeal in two separate criminal cases?

Without obtaining a certificate of probable cause ( 1237.5), defendant filed notices of appeal in both cases, checking the box indicating the appeals were based on the sentences or other matters occurring after the pleas that did not affect the validity of the pleas. This court appointed counsel for defendant on appeal. Appointed counsel filed a brief raising no issues, but requesting this court to independently review the record for arguable contentions pursuant to People v. Wende (1979) 25 Cal.3d 436. Defendant was advised on his right to file a supplemental brief within 30 days. No brief has been received from defendant.