Fix `handle_return` for NVRTC

[leofang]

issue (I think): if nvrtcCreateProgram doesn't return successfully you will have an assertion error in handle_return: https://github.com/NVIDIA/cuda-python/pull/87/files#diff-2a230a37390d371cf14077a7482ce998510b6aa9e52fcbb62d7ace983d996ce4R45

Originally posted by @wence- in #87 (comment)

[leofang]

Also #87 (comment)