sack: don't raise error when non-existing arch is used
sack: don't raise error when non-existing arch is used

Reference: https://github.com/rpm-software-management/libhif/commit/611a86afaa47ce2c84207a602d167eb851a4d19a
Signed-off-by: Igor Gnatenko <71fb2d16c26f553767b965fdac40e83622cad277@redhat.com>

rpm-software-management/hawkey,Conan-Kudo/hawkey,Conan-Kudo/hawkey,Conan-Kudo/hawkey,rpm-software-management/hawkey,rpm-software-management/hawkey,rpm-software-management/hawkey,Conan-Kudo/hawkey