Fix chainAsync() throwing an error

snippets/chainAsync.md

@@ -4,10 +4,12 @@ Chains asynchronous functions.
 
 Loop through an array of functions containing asynchronous events, calling `next` when each asynchronous event has completed.
 
+The tenerary function checks the next function exists before calling it, otherwise it will exit.
+
 ```js
 const chainAsync = fns => {
   let curr = 0;
-  const next = () => fns[curr++](next);
+  const next = () => fns[++curr] ? fns[curr](next) : false;
   next();
 };
 ```