I know that there are several questions posted on here with the same topic and error, but none of them indicate the same problem as mine, so I decided to post my question he
You are using the wrong object to get avatar value here json.getString(KEY_AVA). It should be json_user.getString(KEY_AVA).
avatar
json.getString(KEY_AVA)
json_user.getString(KEY_AVA)
Also, you can use optString instead of getString which just returns null if value doesn't exist, instead of throwing an exception.
optString
getString
null