Build failure with ghc 8.4

```
fb: BuildFailureException Process exited with ExitFailure 1: ./Setup build
yesod-fb: DependencyFailed (PackageName "fb")

Building library for fb-1.2.0..
[ 1 of 17] Compiling Facebook.Types   ( src/Facebook/Types.hs, dist/build/Facebo
ok/Types.o )

src/Facebook/Types.hs:195:40: error:
    Ambiguous occurrence ‘<>’
```

The ambiguous occurrence errors repeat ad infinitum.