Update main.go

Ex:
```go
type User struct {
	ID        int64
	Name      string `sql:"not null;unique"`
	Hobby     []string `sql:"-"`
	HobbyStr  string `sql:"type:text"`
}
u := &User{Name:"ElvizLai"}
fmt.Println(db.Last(u, "5x").RecordNotFound())//should be true but it return false
```
It has error: "Unknown column '5x' in 'where clause'", This maybe also belongs to "RecordNotFound"

main.go

@@ -369,7 +369,7 @@ func (s *DB) NewRecord(value interface{}) bool {
 }
 
 func (s *DB) RecordNotFound() bool {
-	return s.Error == RecordNotFound
+	return s.Error == RecordNotFound || s.Error != nil
 }
 
 // Migrations