Make wrap-exceptions middleware robust against nil response body

Fixes #766

Author: DerGuteMoritz

src/aleph/http/client_middleware.clj

@@ -276,6 +276,12 @@
                           (str "status: " status)
                           (assoc rsp :body (ByteArrayInputStream. body))))))
 
+          (nil? body)
+          (d/error-deferred
+           (ex-info
+            (str "status: " status)
+            rsp))
+
           :else
           (d/chain'
             (s/reduce conj [] body)