isl_tab_compute_reduced_basis: handle empty tables
isl_tab_compute_reduced_basis: handle empty tables

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