Live chart isn't updated when packets aren't captured on Linux #951
Description
The live chart reporting traffic rate on Linux is only updated when packets are being exchanged.
When no packets are captured, the expectation is to see the chart being updated with zeroed values for incoming & outgoing data.
This issue is caused by libpcap's pcap_set_timeout() function, which on Linux triggers the timeout on the capture only when there is some packet in the buffer.
This is a regression introduced with #795, where I'm relying on the timeout to periodically receive capture messages from the backend.
This problem doesn't seem to be present on Windows and macOS.