[llvm-readelf] - Do no print an empty symbol version as "<corrupt>"

It is discussed here https://reviews.llvm.org/D71118#inline-643172

Currently when a version is empty, llvm-readelf prints:
"000:   0 (*local*)       2 (<corrupt>)"

But GNU readelf does not treat empty section as corrupt.
There is no sense in having empty versions anyways it seems, but
this change is for consistency with GNU.

Differential revision: https://reviews.llvm.org/D71243