Error message after logging out and then logging back in

"Actions must be plain objects. Use custom middleware for async actions."

This happened after I signed out in the client and then entered the passphrase to log in back. For some reason it happened only once and currently I can't reproduce it.

```Error: Actions must be plain objects. Use custom middleware for async actions. at _ (file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:1107161) at n (file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:2745672) at file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:2627238 at file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:437820 at _.t [as _dispatch] (file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:2745157) at reduce.forEach.e (file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:224376) at Array.forEach () at _rpcIncoming (file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:224360) at _rpcClient.e (file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:222544) at e (file:///opt/keybase/resources/app/desktop/dist/index.bundle.js:1:454274)```

Start with the desktop application's index.bundle.js stack trace and trace the logout-then-login flow around the incoming RPC dispatch. The report is currently not reproducible, so done would require identifying the cause and confirming that the same sign-out and passphrase login sequence no longer produces the plain-object action error.

Written by the indexing model from the issue text.