fix: logfmt should produce 0 or more extra labels

[akvlad]

Example:
line: INFO: <script>: Reply from Inbound - S=123 - Proxy Authentication Required M=INVITE IP=udp:127.0.0.1:1234 ID=abcd@127.0.0.1
parse result:

{
  S: '123',
  M: 'INVITE',
  IP: 'udp:127.0.0.1:1234',
  ID: 'abcd@127.0.0.1'
}

[akvlad]

e2e passed successfully. Minor update should work ok.