MAC undefined in Linux host

[karimcitoh]

Scanning seems to work on Mac, but when testing on Ubuntu, I get this error:

node_modules/network-list/lib/index.js:45
                        result.mac = mac.replace(/:([^:]{1}):/g, ':0$1:');
                                         ^

TypeError: Cannot read property 'replace' of undefined
    at /home/random/lab/digital-retail-status/node_modules/network-list/lib/index.js:45:42
    at ChildProcess.<anonymous> (/home/random/lab/digital-retail-status/node_modules/node-arp/lib/arp.js:73:5)
    at emitTwo (events.js:126:13)
    at ChildProcess.emit (events.js:214:7)
    at maybeClose (internal/child_process.js:925:16)
    at Socket.stream.socket.on (internal/child_process.js:346:11)
    at emitOne (events.js:116:13)
    at Socket.emit (events.js:211:7)
    at Pipe._handle.close [as _onclose] (net.js:554:12)