fix grey covers

[kongo09]

• check for existence of filtered devices, irrespective of the view configuration
• also include count of known spotify connect devices into total count

addresses #171 and #158

Unfortunately, I have no idea about Typescript development or Node.js so I cannot test this locally. Please take a look ;-)

[kongo09]

Managed to install nvm, tsc and npm and build the thing. My fix works for me.