Minor fixes

Author: nekohasekai

common/buf/alloc.go

@@ -89,7 +89,7 @@ func (alloc *defaultAllocator) Get(size int) []byte {
 // which the cap must be exactly 2^n
 func (alloc *defaultAllocator) Put(buf []byte) error {
 	bits := msb(cap(buf))
-	if cap(buf) == 0 || cap(buf) < 64 || cap(buf) > 65536 || cap(buf) != 1<<bits {
+	if cap(buf) < 64 || cap(buf) > 65536 || cap(buf) != 1<<bits {
 		return errors.New("allocator Put() incorrect buffer size")
 	}
 	bits -= 6

common/udpnat2/conn.go

@@ -8,6 +8,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/buf"
 	"github.com/sagernet/sing/common/canceler"
 	M "github.com/sagernet/sing/common/metadata"
@@ -108,6 +109,7 @@ func (c *natConn) SetTimeout(timeout time.Duration) bool {
 func (c *natConn) Close() error {
 	c.closeOnce.Do(func() {
 		close(c.doneChan)
+		common.Close(c.handler)
 	})
 	return nil
 }