set to default value with config is missing (#7320)

app/user.go

@@ -750,7 +750,7 @@ func GetProfileImage(user *model.User) ([]byte, bool, *model.AppError) {
 	var img []byte
 	readFailed := false
 
-	if len(utils.Cfg.FileSettings.DriverName) == 0 {
+	if len(*utils.Cfg.FileSettings.DriverName) == 0 {
 		var err *model.AppError
 		if img, err = CreateProfileImage(user.Username, user.Id); err != nil {
 			return nil, false, err