Remote Config fetching failure http code 0

* Unity editor version: 2020.3.41f
* Firebase Unity SDK version: 10.0.1
* Source you installed the SDK: Remote Config
* Problematic Firebase Component: Remote Config
* Platform you are using the Unity editor on: Windows
* Platform you are targeting: Android
* Scripting Runtime: IL2CPP

(Please list the full steps to reproduce the issue. Include device logs, Unity logs, and stack traces if available.)
I try to learn how to use Remote Config sample from this repo without network connection.
With sample code
`
public Task FetchDataAsync() {
DebugLog("Fetching data...");
Task fetchTask = Firebase.RemoteConfig.FirebaseRemoteConfig.DefaultInstance.FetchAsync(TimeSpan.Zero);
return fetchTask.ContinueWithOnMainThread(FetchComplete);
}
`
It shows Debug.LogError "fetching failure: http code 0"
Is it behavior by design?
Full stack
`
fetching failure: http code 0
UnityEngine.Debug:LogError (object)
Firebase.Platform.FirebaseLogger:LogMessage (Firebase.Platform.PlatformLogLevel,string) (at /Users/runner/work/firebase-unity-sdk/firebase-unity-sdk/app/platform/Unity/FirebaseLogger.cs:95)
Firebase.LogUtil:LogMessage (Firebase.LogLevel,string) (at /Users/runner/work/firebase-unity-sdk/firebase-unity-sdk/app/src/LogUtil.cs:69)
Firebase.LogUtil:LogMessageFromCallback (Firebase.LogLevel,string) (at /Users/runner/work/firebase-unity-sdk/firebase-unity-sdk/app/src/LogUtil.cs:77)
Firebase.AppUtil:PollCallbacks () (at /Users/runner/work/firebase-unity-sdk/firebase-unity-sdk/android_unity/armeabi-v7a/app/swig/Firebase.App_fixed.cs:4614)
Firebase.Platform.FirebaseAppUtils:PollCallbacks () (at /Users/runner/work/firebase-unity-sdk/firebase-unity-sdk/app/platform/FirebaseAppUtils.cs:33)
Firebase.Platform.FirebaseHandler:Update () (at /Users/runner/work/firebase-unity-sdk/firebase-unity-sdk/app/platform/Unity/FirebaseHandler.cs:208)
Firebase.Platform.FirebaseMonoBehaviour:Update () (at /Users/runner/work/firebase-unity-sdk/firebase-unity-sdk/app/platform/Unity/FirebaseMonoBehaviour.cs:45)
`

#### Steps to reproduce:

1)Disable network
2)Try to click fetch data from sample Remote Config scene