sym is only set for local symbols. h is only set for global symbols. Gas
won't let me create a global section symbol, but bfd appears to have some
support for that, and I can't rule out that other assemblers might do this.
So we need to support both, and verify sym and h are non-NULL before using.
bfd/
PR 24365
* elfnn-riscv.c (riscv_elf_relocate_section): For STT_SECTION check,
verify sym non-NULL before using. Add identical check using h.