'IllegalArgumentException' error regarding ble, uuid

[MakeMeCookie]

I ran the app as it was. However, if you look at the log, there is a "IllgalArgumentException" error, and uuid's
App terminates with an empty character 'IllegalArgumentException: Invalid UUID String'

If this format is not correct, the java.util.UUUID.fromString() method will cause an IllgalArgumentException.
IllegalArgumentException: InvalidUUUID string: The UUID appears to be an empty string after this. This means that the UUID string is either empty or null.

Therefore, to resolve this issue, make sure that the UUID string is correct. Make sure that the UUID string is empty or not null, and that it conforms to the UUID format.

"if (characteristic == null) {
characteric = service.get characteric ("0000ff52-0000-1000-8000-00805f9b34fb");
}"
It looks like this. Why is there an error?