isl_vertices.c: compute_chambers: avoid invalid access on error path
isl_vertices.c: compute_chambers: avoid invalid access on error path

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

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