Add try catch for method update_wg_usage to show propper error cause

[devlifeX]

I faced error in refreshing usage and find out there is not interface hiddifywg running.
This command raised error and not working:
wg_raw_output = subprocess.check_output(['wg', 'show', 'hiddifywg', 'transfer'])
after change port number wireguard in admin panel and apply changes it's worked.

[hiddify-com]

We know it but we want to have error in case of issue so we can find if an error occured