isl_schedule.c: construct_band: with_merged_divs: accept NULL pointer on zero-size allocation
isl_schedule.c: construct_band: with_merged_divs: accept NULL pointer on zero-size allocation

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

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