reserach st: refine key.c

@@ -97,8 +97,9 @@ int st_thread_setspecific(int key, void *value)
 
 void *st_thread_getspecific(int key)
 {
-  if (key < 0 || key >= key_max)
+    if (key < 0 || key >= key_max) {
         return NULL;
+    }
     
     return ((_ST_CURRENT_THREAD())->private_data[key]);
 }