FIx segmentation fault in oned service when configured to cache mode.

Before :
```
        if (!event.empty())
        {
            hm->trigger_send_event(event);
        }
```

After:
```
     if (!nd.is_cache())
    {
        if (!event.empty())
        {
            hm->trigger_send_event(event);
        }
    }
```

When nebula is cache HookManager isn't initialize, therfore ```hm``` equals to null.

(cherry picked from commit 9e6d755d733c6b065327480a56275775e389696c)

src/rm/Request.cc

@@ -460,9 +460,12 @@ void Request::execute(
 
     std::string event = HookAPI::format_message(method_name, pl, att);
 
-    if (!event.empty())
+    if (!nd.is_cache())
     {
-        hm->trigger_send_event(event);
+        if (!event.empty())
+        {
+            hm->trigger_send_event(event);
+        }
     }
 
     if ( log_method_call )