(if) and (if 1) both return nil. JVM clojure throws "Too few arguments to if".
fixed, https://github.com/clojure/clojurescript/commit/9abeb143f66ad6d92756c2dd702966f63ae76c27
fixed, https://github.com/clojure/clojurescript/commit/9abeb143f66ad6d92756c2dd702966f63ae76c27