[NVFuser] don't decompose conv2d if we don't have shape info
Sometimes bias won't have shape info (e.g. in the added test, conv gets run two times in a loop, each with different shapes). In that case we should just skip decomposition instead of erroring out.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77440
Approved by: https://github.com/jjsjann123
