luci-base: sys.lua: fix parsing conntrack entries without timeout

Flow offloaded conntrack entries carry no timeout value and trip up the
record parsing routine. Adjust the code to properly deal with such entries.

Ref: https://forum.openwrt.org/t/offloading-breaks-connections-list/126423
Signed-off-by: Jo-Philipp Wich <jo@mein.io>
(cherry picked from commit 531c0ecff2ca57c4bc0aacee66a0746814fefc78)

modules/luci-base/luasrc/sys.lua

@@ -286,8 +286,14 @@ function net.conntrack(callback)
 
 	local line, connt = nil, (not callback) and { }
 	for line in nfct do
-		local fam, l3, l4, timeout, tuples =
-			line:match("^(ipv[46]) +(%d+) +%S+ +(%d+) +(%d+) +(.+)$")
+		local fam, l3, l4, rest =
+			line:match("^(ipv[46]) +(%d+) +%S+ +(%d+) +(.+)$")
+
+		local timeout, tuples = rest:match("^(%d+) +(.+)$")
+
+		if not tuples then
+			tuples = rest
+		end
 
 		if fam and l3 and l4 and timeout and not tuples:match("^TIME_WAIT ") then
 			l4 = nixio.getprotobynumber(l4)