Includes a empty hosts file drop all hosts

[jeffrey4l]

when includes multi yaml files and when one file has a empty file like below, it will remove all hosts before this file.

# ~/.ssh/assh.yml
inclues:
  - ~/.ssh/assh.d/*.yml

# ~/.ssh/assh.d/temp.yml
hosts: 

DEBUG	Loading config file	{"file": "/home/xxx/.ssh/assh.d/openstack.yml"}
DEBUG	Loaded config file	{"file": "/home/xxx/.ssh/assh.d/openstack.yml", "num-host-before": 130, "num-host-after": 131, "num-host-diff": 1}
DEBUG	Loading config file	{"file": "/home/xxx/.ssh/assh.d/temp.yml"}
DEBUG	Loaded config file	{"file": "/home/xxx/.ssh/assh.d/temp.yml", "num-host-before": 131, "num-host-after": 0, "num-host-diff": -131}
DEBUG	Loading config file	{"file": "/home/xxx/.ssh/assh.d/tt.yml"}
DEBUG	Loaded config file	{"file": "/home/xxx/.ssh/assh.d/tt.yml", "num-host-before": 0, "num-host-after": 9, "num-host-diff": 9}