isl_output.c: print_qpolynomial_c: improve error handling
isl_output.c: print_qpolynomial_c: improve error handling

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

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