Firestore get the document but coroutine handler was called

So im using coroutine on my project, and im trying to get a firestore Document using coroutine await function. And after i got the document, the handler was called even when the job was success. Anyone can explain to me how to fix it?

Here is my code :

val handler = CoroutineExceptionHandler { _, exception ->
            CoroutineScope(Dispatchers.Main).launch {
                Log.e(TAG, "saveData: $exception")
                saveData(mActivity)
            }
        }
CoroutineScope(Dispatchers.IO + handler).launch {
            val document = Firebase.firestore.collection("Users").document(getUID())
                .get().await()
            Log.d(TAG, "saveData: $document")
            withContext(Dispatchers.Main) {
                val currentUser = TemplateUser(
                    getUID(),
                    document.data!!["userName"] as String,
                    document.data!!["userNIS"] as String,
                    document.data!!["userEmail"] as String,
                    document.data!!["userKelas"] as String,
                    document.data!!["kuisSatu"] as Long,
                    document.data!!["kuisSatuAttempt"] as Long,
                    document.data!!["kuisDua"] as Long,
                    document.data!!["kuisDuaAttempt"] as Long,
                    document.data!!["kuisTiga"] as Long,
                    document.data!!["kuisTigaAttempt"] as Long,
                    document.data!!["kuisEmpat"] as Long,
                    document.data!!["kuisEmpatAttempt"] as Long,
                    document.data!!["kuisLima"] as Long,
                    document.data!!["kuisLimaAttempt"] as Long
                )
                Log.d(TAG, "saveData: $currentUser")

            val sharedPreferences =
                mActivity.getSharedPreferences("userProfile", Context.MODE_PRIVATE).edit()
            with(sharedPreferences) {
                putString("userName", currentUser.userName)
                putString("userEmail", currentUser.userEmail)
                putString("userNIS", currentUser.userNIS)
                putString("userKelas", currentUser.userKelas)
                putLong("kuisSatu", currentUser.kuisSatu)
                putLong("kuisDua", currentUser.kuisDua)
                putLong("kuisTiga", currentUser.kuisTiga)
                putLong("kuisEmpat", currentUser.kuisEmpat)
                putLong("kuisLima", currentUser.kuisLima)
                putLong("kuisSatuAttempt", currentUser.kuisSatuAttempt)
                putLong("kuisDuaAttempt", currentUser.kuisDuaAttempt)
                putLong("kuisTigaAttempt", currentUser.kuisTigaAttempt)
                putLong("kuisEmpatAttempt", currentUser.kuisEmpatAttempt)
                putLong("kuisLimaAttempt", currentUser.kuisLimaAttempt)
                apply()
            }
            Log.d(TAG, "saveData: Sharepref berhasil diisi dengan data $document")
            GreetUser.greetUser(mActivity)
        }
    }