Fix LengthEncodedInt returning the length of 1 for an empty slice (#609)

* Fix LengthEncodedInt returning the length of 1 for an empty slice

Author: viciious

mysql/mysql_test.go

@@ -223,3 +223,9 @@ func (t *mysqlTestSuite) TestMysqlUUIDClone(c *check.C) {
 	clone := us.Clone()
 	c.Assert(clone.String(), check.Equals, "de278ad0-2106-11e4-9f8e-6edd0ca20947:1-2")
 }
+
+func (t *mysqlTestSuite) TestMysqlEmptyDecode(c *check.C) {
+	_, isNull, n := LengthEncodedInt(nil)
+	c.Assert(isNull, check.IsTrue)
+	c.Assert(n, check.Equals, 0)
+}

mysql/util.go

@@ -142,7 +142,7 @@ func BFixedLengthInt(buf []byte) uint64 {
 
 func LengthEncodedInt(b []byte) (num uint64, isNull bool, n int) {
 	if len(b) == 0 {
-		return 0, true, 1
+		return 0, true, 0
 	}
 
 	switch b[0] {