I have this exact same problem. Running Mac OS Catalina 10.15.3 on a MacBook Pro 16". Show icon in menu bar is checked in Avast Preferences. This is what I see when the icon is not clicked/clicked. The icon only appears if I click on the area of the menu bar that is blank.
Does anyone know how to fix this, other than to turn off the option to show it in the menu bar altogether?