How to judge the onvif camera is still online?

[LegionFu]

Hello, I want create a application to managing some cameras , and i found a problem when i running the application : if a online camera has disconnected, and i still use this camera reference to visit the camera mycam.media_service.GetProfiles() , the return value is nothing ( not 'None' ) ,my code will stopping execute and skipping the following code ( no errors ) can you help me ?