Do not look for the global early in nullify codegen. The type descriptor can be emitted later and it would raise an error as it could not be found. Use `fir.type_desc` instead so it delays the type descriptor lookup until evrything is emitted. https://github.com/llvm/llvm-project/issues/63775 Reviewed By: vzakhari Differential Revision: https://reviews.llvm.org/D154982