Fix invalid macroexpansion of defcfn without docstring

CHANGELOG.md

@@ -2,6 +2,8 @@
 All notable changes to this project will be documented in this file. This change log follows the conventions of [keepachangelog.com](http://keepachangelog.com/).
 
 ## [Unreleased]
+### Fixed
+- Usage of `defcfn` without a docstring produced an invalid `def` form
 
 ## [0.1.169] - 2021-09-28
 ### Added

src/clj/coffi/ffi.clj

@@ -579,7 +579,8 @@
                                    (mapv (comp symbol name)
                                          (:native-arglist args)))))))
                    (:attr-map args)))
-         ~@(list (:doc args))
+         ~@(when-let [doc (:doc args)]
+             (list doc))
          fun#))))
 (s/fdef defcfn
   :args ::defcfn-args)