Title: mysql_slave: fixed crash if agent output is empty
Level: 1
Component: checks
Class: fix
Compatible: compat
State: unknown
Version: 1.2.8p16
Date: 1483367371

The check will not crash anymore if the agent output does not contain data
for this check. The given state will still be UNKNOWN but with more
comprehensible information like "Item not found in agent output".

