Fix crash if RTCPeerConnection.close() is called twice
Fix crash if RTCPeerConnection.close() is called twice

iFixes: https://github.com/eface2face/cordova-plugin-iosrtc/issues/161

eface2face/cordova-plugin-iosrtc,eface2face/cordova-plugin-iosrtc,BasqueVoIPMafia/cordova-plugin-iosrtc,hit0907/cordova-plugin-iosrtc,eface2face/cordova-plugin-iosrtc,BasqueVoIPMafia/cordova-plugin-iosrtc,hit0907/cordova-plugin-iosrtc,BasqueVoIPMafia/cordova-plugin-iosrtc,hit0907/cordova-plugin-iosrtc