Followup to r8237 (fix for possible crash).

The fixes in r8237 were step in the right direction but were buggy.
That commit should fix the possible crashes.

Thanks to malakudi for taking the time to explain the correct fix
to me.

git-svn-id: http://streamboard.de.vu/svn/oscam/trunk@8239 4b0bc96b-bc66-0410-9d44-ebda105a78c1