In version 1.5 the following message is still populated for bluetooth devices which are known to the system but currently not connected. In my situation the applet tries to read my smartphone which I had connected once to my system.
The only solution is to remove such devices from the bluetooth settings.
The on/off state of my bluetooth connector doesn't affect the error.
glibtop: Failed to open "/sys/class/net/$MACADDRESS/statistics/*": No such file or directory