Dariush vesal

Hi, please review and merge these features. Thanks in advanced.

Missing button icons

4

Hey guys I faced to missing icons on my Kubuntu 18.04 

Add try catch for method update_wg_usage to show propper error cause

2

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...