Fix docs for methods that don't have a return value

Author: John Haley

generate/lib/write_api_docs.js

@@ -120,7 +120,7 @@ var writeApiDocs = function(apiData, path) {
             .join(", ") + ").then(function(" + returnName + ") {\n";
           if (returnName) {
             pageBody += "  // Use " + returnName + "\n";
-          } else if (fdata.return.description) {
+          } else if (fdata.return && fdata.return.description) {
             pageBody += "  // " + fdata.return.description + "\n";
           } else {
             pageBody += "  // method complete"