plugin-x, bug at sample AdMob

cocos2d-x C++
#1

Hello everyone!
After import Admob in multi-platform project, does not build.
With an error:
jni/../../Classes/HelloWorldScene.cpp:115: error: undefined reference to 'vtable for MyAdsListener' collect2.exe: error: ld returned 1 exit status

For class MyAdsListener:

class MyAdsListener : public cocos2d::plugin::AdsListener
{
public:
    virtual void onAdsResult(cocos2d::plugin::AdsResultCode code, const char* msg);
    virtual void onPlayerGetPoints(cocos2d::plugin::ProtocolAds* pAdsPlugin, int points);
};

I changed code:

virtual void onAdsResult(cocos2d::plugin::AdsResultCode code, const char* msg){}
virtual void onPlayerGetPoints(cocos2d::plugin::ProtocolAds* pAdsPlugin, int points){}

and it works
maybe it’s only at me, I don’t know!