Merge pull request facebook#6152 from jimfb/fix-blog-code-fragment

Updated code fragment for correctness.

Author: jimfb

docs/_posts/2015-12-16-ismounted-antipattern.md

@@ -60,14 +60,17 @@ Where `makeCancelable` is [defined by @istarkov](https://github.com/facebook/rea
 const makeCancelable = (promise) => {
   let hasCanceled_ = false;
 
+  const wrappedPromise = new Promise((resolve, reject) => {
+    promise.then((val) =>
+      hasCanceled_ ? reject({isCanceled: true}) : resolve(val)
+    );
+    promise.catch((error) =>
+      hasCanceled_ ? reject({isCanceled: true}) : reject(error)
+    );
+  });
+
   return {
-    promise: new Promise(
-      (resolve, reject) => promise
-        .then(r => hasCanceled_
-          ? reject({isCanceled: true})
-          : resolve(r)
-        )
-    ),
+    promise: wrappedPromise,
     cancel() {
       hasCanceled_ = true;
     },