isl_scheduler.c: intra_dim_map: handle NULL input
isl_scheduler.c: intra_dim_map: handle NULL input

The node passed to intra_dim_map is probably never NULL
in the current code base, but this may change when
intra_dim_map is called on a node extracted from a space
in an upcoming commit.

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

tobig/isl,Meinersbur/isl,inducer/isl-mirror,inducer/isl-mirror,nicolasvasilache/isl,tobig/isl,PollyLabs/isl,nicolasvasilache/isl,nicolasvasilache/isl,inducer/isl-mirror,inducer/isl-mirror,nicolasvasilache/isl,PollyLabs/isl,PollyLabs/isl,PollyLabs/isl,tobig/isl,nicolasvasilache/isl,inducer/isl-mirror,tobig/isl,Meinersbur/isl,Meinersbur/isl,PollyLabs/isl,Meinersbur/isl