hy-iutil: Don't try to unref reldep when it's NULL
hy-iutil: Don't try to unref reldep when it's NULL

Closes: #150
Approved by: cgwalters

hughsie/libhif,rpm-software-management/libdnf,Conan-Kudo/libhif,edynox/libdnf,edynox/libdnf,Conan-Kudo/libhif,hughsie/libhif,rpm-software-management/libdnf,rpm-software-management/libhif,hughsie/libhif,Conan-Kudo/libhif,rpm-software-management/libdnf,Conan-Kudo/libhif,edynox/libdnf,rpm-software-management/libdnf,hughsie/libhif,rpm-software-management/libhif,rpm-software-management/libhif,edynox/libdnf,rpm-software-management/libhif