Don't take empty user as accpeted

knecht.go

@@ -116,6 +116,9 @@ func GetUserData(username string) (*User, []byte, error) {
 				return nil, nil, err
 			}
 		}
+		if userJikan.Data.MalID == 0 {
+			return nil, nil, fmt.Errorf("user returned empty object: %s", username)
+		}
 		// convert to user
 		user = UserConvert(&userJikan)
 		data, err = json.Marshal(&user)