use multi line ternary operator

https://github.com/felixge/node-style-guide#use-multi-line-ternary-operator

lib/adapters/xhr.js

@@ -126,7 +126,9 @@ module.exports = function xhrAdapter(resolve, reject, config) {
   }
 
   // Clean up request
-  requestData = requestData === undefined ? null : requestData;
+  requestData = (requestData === undefined)
+                ? null 
+                : requestData;
   
   // Send the request
   request.send(requestData);