Revert "Lib: Check the description string is NUL-terminated when retrieved"

This reverts commit ed72a1dfc56a4f5428affb1659d6812d54e392c5.

The problem is that the buffer argument might validly be NULL, leading to a
SEGV when we try to check for the NUL termination.

Signed-off-by: David Howells <dhowells@redhat.com>