misplaced :figwheel configuration causes exception

[timothypratley]

Steps to reproduce:

• Add :figwheel {} to the :compiler map of any build
• lein figwheel

Expected:
------ Figwheel Configuration Error ------
Found unrecognized key :figwheel at path (:cljsbuild :builds 1 :compiler)
^^ this works if you us :foo {} instead of :figwheel {}

Actual:
java.lang.Exception: Unable to resolve spec: :figwheel-sidecar.schemas.cljs-options/closure-variable-map-out
... long stacktrace follows