implemented destructor for coap frontend

src/coap-frontend.cpp

@@ -49,6 +49,8 @@ CoapFrontend::CoapFrontend(Controller &controller, uint16_t port) : Frontend(con
 	m_ctxWait.notify_all();
 }
 
+
+
 void CoapFrontend::s_get_index(coap_context_t *ctx UNUSED_PARAM,
 							   struct coap_resource_t *resource UNUSED_PARAM,
 							   const coap_endpoint_t *local_interface UNUSED_PARAM,
@@ -476,6 +478,11 @@ finish:
 
 CoapFrontend::~CoapFrontend()
 {
+	for(auto it = s_callbackMap.begin(); it != s_callbackMap.end(); ++it){
+		if(it->second == this){
+			s_callbackMap.erase(it);
+		}
+	}
 	//cout << __func__ << ": #1" << endl;
 
 	/*