[llvm] [flang][flang-rt] Fix abort on intrinsic assignment from ZLA (PR #177195)

[Peter Klausler via llvm-commits]

klausler wrote:

If the test in question is `Fortran/cray/f90/07/05/zero_len_blank_pad.f90`, it's bad Fortran, and the runtime error is appropriate.

https://github.com/llvm/llvm-project/pull/177195