net-firewall/nftables: backport null payload desc fix
nftables-0.6 handling of payload context descriptions was changed from
version 0.5. This change causes the code to segfault when the desc
variable in payload_expr_pctx_update() is set to null. The issue
appears to be fixed with upstream commit
3503738f77cdbe521da1054a37f59ac2e442b4cf. Therefore, backporting that
commit to 0.6 to fix this issue.
Gentoo-bug: 588192
Package-Manager: portage-2.3.0
Closes: https://github.com/gentoo/gentoo/pull/1865