isl_local_space_get_active: accept NULL pointer on zero-size allocation
isl_local_space_get_active: accept NULL pointer on zero-size allocation

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

tobig/isl,simbuerg/isl,VanirLLVM/toolchain_isl,crossbuild/isl,PollyLabs/isl,Distrotech/isl,inducer/isl-mirror,BenzoSM/isl,BenzoSM/isl,tobig/isl,nicolasvasilache/isl,KangDroidSMProject/ISL,nicolasvasilache/isl,VanirLLVM/toolchain_isl,jleben/isl,UBERTC/isl,simbuerg/isl,inducer/isl-mirror,jleben/isl,abduld/isl,tobig/isl,Meinersbur/isl,SaberMod/isl-current,BobSaget-Mod/libisl,tobig/isl,jleben/isl,Distrotech/isl,Meinersbur/isl,BenzoSM/isl,Meinersbur/isl,PollyLabs/isl,Distrotech/isl,jleben/isl,cfx-next/toolchain_isl-upstream,crossbuild/isl,VanirLLVM/toolchain_isl,UBERTC/isl,evaautomation/isl,SaberMod/isl-current,simbuerg/isl,cfx-next/toolchain_isl-upstream,KangDroidSMProject/ISL,cfx-next/toolchain_isl-upstream,KangDroidSMProject/ISL,SaberMod/isl-current,nicolasvasilache/isl,BobSaget-Mod/libisl,cfx-next/toolchain_isl-upstream,evaautomation/isl,UBERTC/isl,crossbuild/isl,simbuerg/isl,abduld/isl,inducer/isl-mirror,simbuerg/isl,PollyLabs/isl,inducer/isl-mirror,evaautomation/isl,KangDroidSMProject/ISL,BenzoSM/isl,UBERTC/isl,nicolasvasilache/isl,Distrotech/isl,evaautomation/isl,BobSaget-Mod/libisl,PollyLabs/isl,KangDroidSMProject/ISL,VanirLLVM/toolchain_isl,BobSaget-Mod/libisl,PollyLabs/isl,jleben/isl,cfx-next/toolchain_isl-upstream,abduld/isl,BobSaget-Mod/libisl,SaberMod/isl-current,Meinersbur/isl,abduld/isl,Distrotech/isl,VanirLLVM/toolchain_isl,inducer/isl-mirror,BenzoSM/isl,nicolasvasilache/isl,crossbuild/isl