[PATCH nft 0/3] fix crash bug during rule restore

[Florian Westphal <fw@xxxxxxxxx>]

https://bugzilla.netfilter.org/show_bug.cgi?id=1351 

nft -f <<EOF
flush ruleset       

table inet filter {
}
table inet filter {
      chain test {
        counter
    }
}
EOF

segfaults during error reporting.
First patch makes error handling more robust.
Second patch passes the right handle -- with above ruleset this
highlights "chain test" in the resulting error message.

Last patch skips rule cache updates for invalid op to restore
the 0.9.0 behaviour.