Exception when comparing PartialFn to nil

[khardenstine]

(= (r/partial identity 1) nil)
=> util.cljs:117 Uncaught TypeError: Cannot read property 'f' of null
    at reagent.impl.util.PartialFn.cljs$core$IEquiv$_equiv$arity$2 (util.cljs:117)
    at Object.cljs$core$_equiv [as _equiv] (core.cljs:695)
    at Function.cljs.core._EQ_.cljs$core$IFn$_invoke$arity$2 (core.cljs:1257)
    at cljs$core$_EQ_ (core.cljs:1247)

This should just return false.

Using v0.7.x, but its definitely an issue on HEAD too.