isl_union_map.c: cond_un_op: drop needless error label
isl_union_map.c: cond_un_op: drop needless error label

This simplifies the code somewhat.

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

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