Make wrap-exceptions robust against nil response

This happens when the connection is destroyed (via `:aleph/close true`). Without this patch, we'd
always leak a deferred here.

Author: DerGuteMoritz

src/aleph/http/client_middleware.clj

@@ -261,35 +261,36 @@
   [client]
   (fn [req]
     (d/let-flow' [{:keys [status body] :as rsp} (client req)]
-      (if (unexceptional-status? status)
-        rsp
-        (cond
-
-          (false? (opt req :throw-exceptions))
+      (when (some? rsp) ; will happen when `:aleph/close true` is set in req
+        (if (unexceptional-status? status)
           rsp
+          (cond
+
+            (false? (opt req :throw-exceptions))
+            rsp
 
-          (instance? InputStream body)
-          (d/chain' (d/future (bs/to-byte-array body))
-                    (fn [body]
-                      (d/error-deferred
-                        (ex-info
+            (instance? InputStream body)
+            (d/chain' (d/future (bs/to-byte-array body))
+                      (fn [body]
+                        (d/error-deferred
+                         (ex-info
                           (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)
-            (fn [body]
-              (d/error-deferred
+            (nil? body)
+            (d/error-deferred
+             (ex-info
+              (str "status: " status)
+              rsp))
+
+            :else
+            (d/chain'
+             (s/reduce conj [] body)
+             (fn [body]
+               (d/error-deferred
                 (ex-info
-                  (str "status: " status)
-                  (assoc rsp :body (s/->source body)))))))))))
+                 (str "status: " status)
+                 (assoc rsp :body (s/->source body))))))))))))
 
 (defn wrap-method
   "Middleware converting the :method option into the :request-method option"