Update docusign.js

Fix for production issue getting following error and node.js crashes.

--------
/home/node/tc-api/actions/docusign.js:418
           textTabs.push({tabLabel : 'TopCoder Handle', value: user.handle});
                                                                   ^
TypeError: Cannot read property 'handle' of undefined
   at async.waterfall.envelopeId (/home/node/tc-api/actions/docusign.js:418:77)
   at fn (/home/node/tc-api/node_modules/async/lib/async.js:582:34)
   at Object._onImmediate (/home/node/tc-api/node_modules/async/lib/async.js:498:34)
   at processImmediate [as _immediateCallback] (timers.js:345:15)

actions/docusign.js

@@ -414,7 +414,11 @@ exports.generateDocusignViewURL = {
                             value: tabs[x][1]
                         });
                     }
-
+
+                    if(!user) {
+                        cb(new IllegalArgumentError("*********** Could not find user. *********** DOCUSIGN.JS"));
+                        return;
+                    }
                     textTabs.push({tabLabel : 'TopCoder Handle', value: user.handle});
 
                     //Prepare the POST parameters