isl_tab_pip.c: context_gbr_detect_equalities: improve error handling
isl_tab_pip.c: context_gbr_detect_equalities: improve error handling

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

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