Fix return nil addr in conn

transport/hysteria/protocol.go

@@ -394,7 +394,7 @@ func (c *Conn) Read(p []byte) (n int, err error) {
 }
 
 func (c *Conn) LocalAddr() net.Addr {
-	return nil
+	return M.Socksaddr{}
 }
 
 func (c *Conn) RemoteAddr() net.Addr {
@@ -502,7 +502,7 @@ func (c *PacketConn) WriteTo(p []byte, addr net.Addr) (n int, err error) {
 }
 
 func (c *PacketConn) LocalAddr() net.Addr {
-	return nil
+	return M.Socksaddr{}
 }
 
 func (c *PacketConn) RemoteAddr() net.Addr {

transport/v2raygrpc/conn.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/sagernet/sing-box/common/baderror"
 	"github.com/sagernet/sing/common"
+	M "github.com/sagernet/sing/common/metadata"
 	"github.com/sagernet/sing/common/rw"
 )
 
@@ -62,11 +63,11 @@ func (c *GRPCConn) Close() error {
 }
 
 func (c *GRPCConn) LocalAddr() net.Addr {
-	return nil
+	return M.Socksaddr{}
 }
 
 func (c *GRPCConn) RemoteAddr() net.Addr {
-	return nil
+	return M.Socksaddr{}
 }
 
 func (c *GRPCConn) SetDeadline(t time.Time) error {

transport/v2raygrpclite/conn.go

@@ -15,6 +15,7 @@ import (
 	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/buf"
 	"github.com/sagernet/sing/common/bufio"
+	M "github.com/sagernet/sing/common/metadata"
 	"github.com/sagernet/sing/common/rw"
 )
 
@@ -138,7 +139,7 @@ func (c *GunConn) Close() error {
 }
 
 func (c *GunConn) LocalAddr() net.Addr {
-	return nil
+	return M.Socksaddr{}
 }
 
 func (c *GunConn) RemoteAddr() net.Addr {

transport/v2rayhttp/conn.go

@@ -16,6 +16,7 @@ import (
 	"github.com/sagernet/sing/common/bufio"
 	E "github.com/sagernet/sing/common/exceptions"
 	F "github.com/sagernet/sing/common/format"
+	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 )
 
@@ -174,11 +175,11 @@ func (c *HTTP2Conn) Close() error {
 }
 
 func (c *HTTP2Conn) LocalAddr() net.Addr {
-	return nil
+	return M.Socksaddr{}
 }
 
 func (c *HTTP2Conn) RemoteAddr() net.Addr {
-	return nil
+	return M.Socksaddr{}
 }
 
 func (c *HTTP2Conn) SetDeadline(t time.Time) error {