499: not a valid header (no content-length) issue

[antoniofacchi]

Describe the bug
When I start a new back-end I get:

499: not a valid header (no content-length)
got: Couldn't connect to UNIX-socket at /usr/local/nagios/var/rw/live: Connection refused at /usr/share/thruk/lib/Monitoring/Livestatus.pm line 1134, line 1.

Thruk Version
I'm using these version:
Thruk 3.0.4
Nagios 4,5,0
Livestatus 1.5.0.p12
To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.