using braces, whole nextTick conditioned

amdefine.js

@@ -120,9 +120,11 @@ function amdefine(module, requireFn) {
                 });
 
                 //Wait for next tick to call back the require call.
-                process.nextTick(function () {
-                    if (callback) callback.apply(null, deps);
-                });
+                if (callback) {
+                    process.nextTick(function () {
+                        callback.apply(null, deps);
+                    });
+                }
             }
         }