fix nmcli output split

tests/test_dns_records.py

@@ -24,7 +24,7 @@ def get_dns_servers() -> set:
         _, output = subprocess.getstatusoutput(
             "nmcli -f all device show | grep IP4.DNS | awk '{ print $2 }'"
         )
-        servers = output.split("\n")
+        servers = [l for l in output.split("\n") if l]
 
     if not len(servers):
         # resolvconf