netfilter: nf_conntrack_sip: Allow ct_sip_get_header() to be called with a null ct argument

Signed-off-by: NSimon Horman <horms@verge.net.au>
Acked-by: NJulian Anastasov <ja@ssi.bg>

net/netfilter/nf_conntrack_sip.c

@@ -152,6 +152,9 @@ static int parse_addr(const struct nf_conn *ct, const char *cp,
 	const char *end;
 	int ret = 0;
 
+	if (!ct)
+		return 0;
+
 	memset(addr, 0, sizeof(*addr));
 	switch (nf_ct_l3num(ct)) {
 	case AF_INET: