I think there is a bug in the logout callback, when using it with Kotlin.
The error is:
Caused by: java.lang.IllegalArgumentException: Parameter specified as non-null is null: method kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull, parameter payload
[...]
at com.auth0.android.provider.LogoutManager.resume(LogoutManager.java:55)
at com.auth0.android.provider.WebAuthProvider.resume(WebAuthProvider.java:531)
at com.auth0.android.provider.AuthenticationActivity.deliverAuthenticationResult(AuthenticationActivity.java:129)
at com.auth0.android.provider.AuthenticationActivity.onResume(AuthenticationActivity.java:90)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1446)
at android.app.Activity.performResume(Activity.java:7939)
It looks like the error is that LogoutManager.resume(LogoutManager.java:55) is called like this
callback.onSuccess(null);
but the BaseCallback.void onSuccess(T payload);
is specified as non null.