Android 8 permission issue

I am experiencing the following error in my game and also in new empty projects on Unity 5.6.1p1:

E/Unity: Unable to query for permission: Fragment null must be a public static class to be properly recreated from instance state.”

On the official Android O on my Nexus 6P which was released about a month ago. Its very simple to reproduce. After creating a new project, go into the player settings for Android and set Write Permissions to External, then hit Build and Run on an Android O device. When the app opens, rather than asking if the user will allow it to use the storage, there will just show a black screen. This does not happen on Android 6 and 7.

To get around this error, I can open the app settings in Android and manually toggle the Storage permission on, then the game will load up correctly.

Also my Android sdk is on 26 and Unity is set to use the highest sdk version installed.

Does anyone know why this is happening or any potential causes?

It turns out to be a Unity bug and Unity is aware of the issue.
You can follow this post to keep updated:

https://forum.unity3d.com/threads/game-does-not-work-on-new-android-oreo.490142/