Med: attr: fix derefence of unspecified value pointer

Jumping to out_close out of (site->type == ARBITRATOR) condition means:

• site is not NULL at that point
• tpt pointer hasn't been initialized, yet

-> segfault/read-write access to inappropriate data (depending on the

state the stack was in, most probably the former)

Discovered-by: static analysis/Coverity
Signed-off-by: Jan Pokorný <jpokorny@redhat.com>