What is the current state of the law in relation to a motion brought by defendant's appointed counsel pursuant to People v. Wende?

On March 17, 2015, defendant's appointed counsel filed a brief pursuant to People v. Wende (1979) 25 Cal.3d 436 (Wende) in which no issues were raised. The brief included a declaration from counsel that she had reviewed the record and had sent defendant a letter advising him of her intention to file a Wende brief and that he could file a supplemental brief if he chose to do so. That same day, this court sent defendant a letter advising him that a Wende brief had been filed and that he had 30 days to submit a brief or letter raising any issues he wished this court to consider. Defendant did not file a supplemental brief.