fix(devices): Fixes a JS error when no audio/video is selected and there is a device update.

modules/devices/mediaDeviceHelper.js

     const selectedAudioInputDeviceId = getUserSelectedMicDeviceId(APP.store.getState());
     const selectedAudioInputDevice = availableAudioInputDevices.find(
         d => d.deviceId === selectedAudioInputDeviceId);
-    const localAudioDeviceId = localAudio.getDeviceId();
+    const localAudioDeviceId = localAudio?.getDeviceId();
     const localAudioDevice = availableAudioInputDevices.find(
         d => d.deviceId === localAudioDeviceId);
 
     const selectedVideoInputDeviceId = getUserSelectedCameraDeviceId(APP.store.getState());
     const selectedVideoInputDevice = availableVideoInputDevices.find(
         d => d.deviceId === selectedVideoInputDeviceId);
-    const localVideoDeviceId = localVideo.getDeviceId();
+    const localVideoDeviceId = localVideo?.getDeviceId();
     const localVideoDevice = availableVideoInputDevices.find(
         d => d.deviceId === localVideoDeviceId);