Title: Catch exception when check plugins do not return a state
Level: 1
Component: core
Class: fix
State: unknown
Version: 1.2.5i1
Date: 1387363842
Targetversion: future

When a broken check plugin does not return a proper state then
Check_MK broke with an exception. This is now better handled.
The check now goes into <i>UNKNOWN</i> state with the message
<tt>Check plugin did not return any result</tt>.
